Tire Pressure....

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,812
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Telford
Many (?most) riders here don't anywhere near double their average speed when they go electric. My average speed on an ebike till last week was below what it was on a regular bike 10 years ago. My highest speed (downhill unassisted) is also a little lower because I'm more careful than I was.

(My average speed right now is well under 1mph, not on a bike as I've irritatingly and painfully ruptured my knee tendon, so no bike for several months.)
I noticed something too. My brakes never wear out when I park my bike in the garage. I have some bikes in my shed too that I haven't used for ten years. They've stayed stopped the whole time and whenever I check the brake pads, they don't need replacing. Let's see if the equation from physics can explain that. Work done by the brakes to keep my bikes in the shed is 1/2 × M x V x V. M=20, V = 0, so work done by the brakes = 0.5 x 20 x 0 x 0 = 0. There, zero work done means zero wear. I knew there had to be a reason! If I had know that before I could have taken off the expensive disc brakes, sold them off on Ebay and fitted cheapo rim brakes. I'd be £100 better off. I feel like an idiot now.
 
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thelarkbox

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Aug 23, 2023
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oxon
I am not sure what is it about big black plastic boxes that attract so many people. It is just a bad idea. Making savings on safety is just a false economy. Changing pressure in tyres will make a little difference. Try proper panniers and you will see the difference.
I see what you mean about shifting to a lower centre of gravity for stability, but stability isnt the issue, the front box may look big but its not for the heavy stuff as a rule.

The attraction to me at least of the black plastic box is not only are they cheap but they help make the bike look cheap too no one wants a nice expensive looking bike round here unless they can keep it securely locked up 100% of the time its not in use. but if left locked with a gold d lock or like in my case a 4ft oxford mororcycle lock if its nice it will get nicked.. wish my bike wld hurry up n get scuffed sometimes..

@saneagle so i will be consuming more brake pads.. ok. as an x 'real biker' got a 1976 honda cb750 F1 project ready to start ( well under a blanket in the garage..) .. a brake check and adjustment if needed is already a habit.
 

Cadence

Esteemed Pedelecer
Feb 23, 2023
273
204
My experience since getting into this e-bikery is that saneagle is absolutely right. Quite apart from the fact that I inevitably ride faster than I did before, the added mass and momentum of motor and battery means that slowing and stopping downhill requres a lot more braking force. If I was starting from scratch I would definitely be looking at hydraulic discs.
As I'm stuck with v-brakes, my main concern is rim wear. I've concluded that I would rather wear out brake pads than rims and found that some pads (Shimano in particular) are too hard and seem to grind the aluminium rims into a black shimmery paste. I bought some cheap no-brand cartridge holders with multi-coloured pads off ebay which stopped the bike OK but wore down very quickly. The rims stayed clean though.
I'm currently using BBB Tristop and they do the same - stop well, wear out quickly but are kind to the rims. Koolstop Salmon pads seem to get a lot of good reviews, but they are rather expensive if they have to be changed frequently.
 
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guerney

Esteemed Pedelecer
Sep 7, 2021
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@guerney 47 kph! without warning.. My fillings are coming out in sympathy..
I'm hoping living vicariously through my GoPro (see video below, 1080P is selectable) won't finish the job! The camera removed some of the shaking. That set of potholes was longer than depicted in 4 frames, must have been there ages to have grown so large. I slowed down a little before bouncing over them. I'm in the process of tightening up the light knocked loose.


The energy you have when moving on a bicycle is 1/2 x mass x velocity x velocity. That means if you double your average speed, you have four times your previous average energy, and your brakes have to do four times as much work to dissipate it, so brakes that work fine on a normal bike can be quite inadequate when you add a motor and battery. The more work the brakes do, the faster they wear out, the faster they wear the rims and the quicker they go out of adjustment.

Let's say you bike weighed 15 kg, you were 85 kg and travelling at 4 m/s (9 mph). Your energy would be 800 Joules. Now add 6kg electric kit, 5kg of locks and 3kg of luggage and you now travel at 6 m/s (13.5 mph). Your new energy would be 2052 Joules. That's 256% of the work that the brakes had to do before and 256% wear.
Thanks @saneagle, that's a good and timely reminder to avoid the free gift of speed from gravity, but there are over 4.5 miles along that route with effortless long straight downhill runs plus lots of exciting twisty bends, the experience of which reminds me of riding my old motorbike. Simply couldn't resist. I exceeded 47kph in parts, but didn't glance at the speedo much, and the GoPro was set to "Linear" rather than "Superwide", so missed view of it. I'm amazed my 17 year old Dahon Helios 20" wheeled folding bike with rim brakes, hasn't snapped in half yet. It's a jolly good thing I didn't have to brake at that speed. Many here with their cooler MTBs and other bikes wouldn't give this sort of thing a second's thought lol. For motorbike riders, it's a total non-event!




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Az.

Esteemed Pedelecer
Apr 27, 2022
2,044
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Plymouth
The attraction to me at least of the black plastic box is not only are they cheap but they help make the bike look cheap too
I take panniers to the shop with me, so they don't attract unwanted attention.

I took a car to the mechanic few days ago and paid £200 to fix a puncture. For £200 you can have a hybrid or mountain bike in mint condition bought on Ebay. Bicycles are super cheap comparing to other means of transport. Your bike is not designed to deal with potholes and heavy cargo and inflating/deflating tyres wont change that. Plastic boxes only make things worse.
You already had a near miss - learn the lesson.

As per brakes - hydraulic discs are a way to move forward. Saving on safety is a false economy.
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,209
371
oxon
Many (?most) riders here don't anywhere near double their average speed when they go electric. My average speed on an ebike till last week was below what it was on a regular bike 10 years ago. My highest speed (downhill unassisted) is also a little lower because I'm more careful than I was.

(My average speed right now is well under 1mph, not on a bike as I've irritatingly and painfully ruptured my knee tendon, so no bike for several months.)
Sorry to hear about the knee Hope you have a speedy and full recovery..

Im just grateful my first few journeys were on quiet empty streets and tracks and not busy traffic filled roads.

My future e-biking will lets just say different from my initial expectations and probably like yourself on average a lil slower.

@guerney .. thats a push bike your ridding? looks more like the sight seen thru a visor of a full faced helmet on a motorbike. My bike is not in the same class as yours.. nor would i want it to be, not without full clobber, road rash or chin bump at those speeds OUCH!!

RIM WEAR???? WTF? so why no steel rims or 1mm thick 316 plates epoxied onto the soft ally??
RIM WEAR?? REALLY!! If i manage to hold onto a bike for more than a a couple of years then perhaps i will look at changing brake blocks and my hand lives on the front brake at tension if even slightly down hill, currently the 3yr old bikes blocks look ok about 1/3 -1/2worn as of fitting the hub motor?? didnt even bother looking at the back blocks..
OK IM CONVINCED!! ebike #2 disk brake on the front. AND Full Faced lid n leathers if approaching the speeds @guerney coasts at.

All my local cycling to date is in town, round the ring rd cycle tracks, and riverside bridle paths. with few opportunities to go full pelt. The top gear of my bike as was (since added a smaller top gear 11t) a 36:14 ratio.
The few steep hills around require partial brake descent at all times no freewheeling unless you want problems.. and i never was nor never will be sporty sporty, I did like my club paragliding and caving, but im not a racer or slim. when going into the city i take a route of wooded footpaths shared with pedestrians and dog walkers so not a fast route.
All of which my style of cylce is ideal for.

What my cycle is not good for is racing faster.. doh!

what the ebike hub motor is great for is pushing me up the hill home after going out on the bike.. what its not good for is speeding beyond the bikes and or my capacity to handle on dodgy roads. Mia Culpa

@Az I both hear and agree with you. and any plans to carry more than what i have been carrying 'happily' with leg power does involve pannier type capacity. but the nice big sturdy panniers cost more than the £200 ebay special bikes you mention. or close to it new.. Im not saying they are not worth it ...
But i have left over fibreglass and resin cortex sheet a fair few meters of strong elastic cord and paracord and ideas (untested as yet).. but are along the lines of a hook on/clip on curved 3d sheet of material laced with an elastic knotted net with hooks to the rear, Unhook net, place bag/box within the curve and stretch n hook the net tight n go..
I will probably exhaust my supplies in design and testing and end up spending 8x if pursued beyond what i have in stock, but thats the way midnight ideas and fun projects go at times..

and for current use demands, shopping wise one heavy bag for the back and one lighter delicate bag for the front and im set, as long as i keep to REASONABLE SPEEDS and keep my inner boy racer at bay..
The street i lost my luggage in is at the top of a hill thats a length of cycle path that runs alongside the slip road that joins the ring rd from an under bridge roundabout. circa 500m uphill , ist time i cruised up @15mhp via e power i turned into the rough bumpy street @ full speed and lost it.. Mia culpa - all on me.. I was lucky.. I lost the pop out of the back box and the loo roll from the front which bounced of a parked car, i slammed on the brakes and picked up everything.
At no time in the past decade+ have i ridden up that incline at full pelt, i can manage it in top gear with no extra mass, but its at a very slow cadence and im puffed at the top and slow, when the boxes are full in in 2nd or 3rd gear, sometimes 4th.. i do like to push myself a lil on occasion.. but always puffed at the top. and by the time im rolling round the corner into the street in question im only starting to think about gaining speed and i usually dont get up past what was 5th gear of a 6speed by the time im turning off that circa 1 mile rd its nominally uphill only noticeable if pedaling puffed tho ;)
Lots of folk with bikes walk up that slip rd incline pushing, I have too on occasion, but its designed in short ramps and gentler inclines in-between so suits an unfit bod like me who can push themselves for a short period but cant keep it up ;) its one hill i may return to pedaling up to once the novelty of the e-bike has passed as its the last real hill on my way home from the supermarket and has been my token gesture to exercise for the last few years.. then again its SOOOOO very nice to get home NOT PUFFED..
 

guerney

Esteemed Pedelecer
Sep 7, 2021
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@guerney .. thats a push bike your ridding? looks more like the sight seen thru a visor of a full faced helmet on a motorbike. My bike is not in the same class as yours.. nor would i want it to be, not without full clobber, road rash or chin bump at those speeds OUCH!!
I'm quite a cautious rider, unless there's a tempting downhill. I potter about at 25kmh or slower the rest of the time, unless I need some exercise and pedal beyond the PAS cutoff speed. It's a basic old Dahon, nothing special. There's no way to fit suspension or disc brakes.


I use a jawguarded helmet, but any more clobber than that (I've got kneepads, elbow pads in stainless steel, which I very occasionally use when not wearing a leather biker jacket covered by a hiviz blouson) and I'd end up looking like "Monster" branded fully armoured @soundwave, who has recently bought shoulder pads - unsure if they're 80s shoulder pads, but hope so.
 
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guerney

Esteemed Pedelecer
Sep 7, 2021
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(My average speed right now is well under 1mph, not on a bike as I've irritatingly and painfully ruptured my knee tendon, so no bike for several months.)
That sounds nasty, why did you do that? Does/did it require surgery? Did it happen skiing or skydiving?
 

soundwave

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May 23, 2015
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sjpt

Esteemed Pedelecer
Jun 8, 2018
3,832
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That sounds nasty, why did you do that? Does/did it require surgery? Did it happen skiing or skydiving?
Yes, surgery yesterday. (At the computer now reading forums to keep my mind off it, but not too bad really.) Not quite so exotic as you suggest. We'd hung our inner tent up to dry on the stairs (Our daughter and son-in-law had borrowed it for a festival and the last day it rained, typical). I was pushing the tent off the bannisters and slipped on the stairs.

My wife knew the ropes, having broken her kneecap in a 0mph tandem slip a couple of years ago.
 

Saracen

Esteemed Pedelecer
Aug 24, 2023
532
61
Is is not "Tyre" and not Tire, you Tire when running ;)
 

guerney

Esteemed Pedelecer
Sep 7, 2021
11,390
3,234
Yes, surgery yesterday. (At the computer now reading forums to keep my mind off it, but not too bad really.) Not quite so exotic as you suggest. We'd hung our inner tent up to dry on the stairs (Our daughter and son-in-law had borrowed it for a festival and the last day it rained, typical). I was pushing the tent off the bannisters and slipped on the stairs.

My wife knew the ropes, having broken her kneecap in a 0mph tandem slip a couple of years ago.
Darn, tendons and ligaments take ages to heal - if you don't use them enough they don't heal, and if you use them too much they get damaged. Blood supply is by osmosis, not directly veined or arteried. My right knee still isn't right 18 years after hitting a black BMW and losing that fight... which is one of my excuses for setting my BBS01B converted bike's firmware so it behaves like a throttle-less moped lol: Ghost pedal for a moment or two on a very low gear and away it accelerates to 25kph, and keeps you there with zero effort for 43 miles of mixed road terrain. It's easy on the knees.
 
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chris667

Pedelecer
Apr 7, 2009
164
108
A couple of thoughts:
  1. I run my 26 x 1.75front/26 x 2.25rear tyres at 55psi and it feels right to me - my combined system weight is about the same as yours.
  2. You should be thinking about tyre choice as well as tyre pressure, and remember your back wheel's carrying two and a half times as much weight as the front. As well as being dished! There is nothing wrong with having a wider tyre on the back - it's actually better engineering.
  3. I suspect that if you have a more supple/thin sidewall on your tyre, you're more likely to experience "snakebite" punctures, or at least that's been my experience. Back in my roadie days I generally chose Panaracer Paselas because they were more comfortable than Marathons but I definitely got more punctures. I have Specialized Crossroads on my back wheel now which I like but I don't think you can buy them anymore.
  4. V brake rims are adequate for a bike that's used on the road, but if you are riding through a lot of mud will inevitably cause more wear. I have them on my bike because they're easy to work on and I understand them properly, but mostly because I'm a tightwad and I had some. Discs would be less faff but I am happy with what I have and they stop me anywhere in the Peaks.
  5. Definitely pannier bags - keeps the weight lower down, and if you're in a high crime area they can come with you when you get off the bike! A trailer might be an idea too - I have always loved the idea of unclipping a trailer to go round the shops.
 

FJC71

Pedelecer
Mar 1, 2020
47
16
I usually work out tyre pressure based upon the 15 % tyre drop rule as discussed in Bicycle quarterly PDF article I downloaded some years ago attached.

Taking your overall weight as 130Kg and your bike as a city bike weight distribution 35% front 65% rear. (could be worse on an e bike) The graph would give some interesting results.

The graph gives a line based on 37mm tire width not 40 as you have.

Front load 45.5 Kg @ 37mm tyre width approx 37.75psi
Rear Load 84.5 Kg @ 37mm tyre width, off the graph but extending the line it looks to be around 85psi.
 

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saneagle

Esteemed Pedelecer
Oct 10, 2010
6,812
3,150
Telford
RIM WEAR???? WTF? so why no steel rims or 1mm thick 316 plates epoxied onto the soft ally??
RIM WEAR?? REALLY!! If i manage to hold onto a bike for more than a a couple of years then perhaps i will look at changing brake blocks and my hand lives on the front brake at tension if even slightly down hill, currently the 3yr old bikes blocks look ok about 1/3 -1/2worn as of fitting the hub motor?? didnt even bother looking at the back blocks..
OK IM CONVINCED!! ebike #2 disk brake on the front. AND Full Faced lid n leathers if approaching the speeds @guerney coasts at.
You will see that your brake blocks and rims wear much faster now. Many people have tried to beat the laws of physics, but, so far, none have succeeded. Maybe you'll be the first.
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
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371
oxon
You will see that your brake blocks and rims wear much faster now. Many people have tried to beat the laws of physics, but, so far, none have succeeded. Maybe you'll be the first.
Better forewarned than surprised and caught short with no brake blocks. And on consideration it makes a lot of sense too. Im very impressed with the power delivery from my kit even as the smaller battery option looses voltage, it moves my mass at an impressive acceleration when asked, and as a result i have been heavy with the brakes to compensate..

@FJC71, Thanks for the info, ive downloaded and archived it. and after a quick read through Im feeling quite vindicated and feel like printing it out and marching it upto the h/w shop where my doubt was born..
(not that i will of course..)

"Give me the raised eyebrow will ya?? Check this out buddy boy!!" Is what i would say if the place was not staffed by some very patient bods who spend all day listening to customers who dont know what they want half the time, and always with a smile.

edit - AND i will be putting some air into the back wheel tomorrow pronto.. its been a lil nerve wreaking bottoming out all too frequently the last day or so with lower pressure in the back tire especially.

odd aside - As a kid cycling i could maintain awareness or at least i felt like i could while monitoring my back wheels travel on the ground comfortably on the cycle track, I try that now and im spooked and looking back up before i can even focus on the damn wheel..
 
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Bikes4two

Esteemed Pedelecer
Feb 21, 2020
1,006
432
Havant
The attraction to me at least of the black plastic box is not only are they cheap but they help make the bike look cheap too no one wants a nice expensive looking bike round here unless they can keep it securely locked up 100% of the time its not in use
I'm with you on that one @thelarkbox - I'm all for stealth where possible - most ebikes are so glaringly obvious from the permanently on bright front light, the large handlebar display and often some gert great Hailong battery pack on a downtube: all saying to the scrots in the world, "come and get me".

Nothing is safe from the determined thief but you can mitigate the risk and who wants to steal a plastic box.

Off topic a little - below is my £140 2nd hand bike with one battery in the handlebar bag (8.7Ah) and the 'booster' battery (4.3Ah) in the seat tube bottle cage tool holder and of course the TSDZ2 mid drive motor 'hiding' behind the chain wheel. When out with my club mates I love parking my bike alongside their £mega machines :cool: .

53581
 
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thelarkbox

Esteemed Pedelecer
Aug 23, 2023
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@Bikes4two It takes more than a single double take to spot that motor.. especially if your whooshing by.

mine? significantly less stealthy.. but still looks cheaper than yours ;)
 
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thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,209
371
oxon
A couple of thoughts:
  1. I run my 26 x 1.75front/26 x 2.25rear tyres at 55psi and it feels right to me - my combined system weight is about the same as yours.
  2. You should be thinking about tyre choice as well as tyre pressure, and remember your back wheel's carrying two and a half times as much weight as the front. As well as being dished! There is nothing wrong with having a wider tyre on the back - it's actually better engineering.
  3. I suspect that if you have a more supple/thin sidewall on your tyre, you're more likely to experience "snakebite" punctures, or at least that's been my experience. Back in my roadie days I generally chose Panaracer Paselas because they were more comfortable than Marathons but I definitely got more punctures. I have Specialized Crossroads on my back wheel now which I like but I don't think you can buy them anymore.
  4. V brake rims are adequate for a bike that's used on the road, but if you are riding through a lot of mud will inevitably cause more wear. I have them on my bike because they're easy to work on and I understand them properly, but mostly because I'm a tightwad and I had some. Discs would be less faff but I am happy with what I have and they stop me anywhere in the Peaks.
  5. Definitely pannier bags - keeps the weight lower down, and if you're in a high crime area they can come with you when you get off the bike! A trailer might be an idea too - I have always loved the idea of unclipping a trailer to go round the shops.
Cheers Chris, The came with bike tires are as you suggest a lil thin walled, so for the new motor wheel I splurged on a shwarbe? us brand, Road Guard tire at about 2x the cost of a cheapie black option, even paid the diddy premium for a cream coloured one too ;) its even got a reflective strip built in fancy eh ?

Since landing in here and browsing what some folk have done and are doing with trailers etc, and with the added oomph a hub motor provides to get underway Yes i agree thats certainly an attractive option and possibly a better one than saddling up the sides of my bike with diy concoctions ..