Hub motor and V brakes - how long will the rim last?

[Klang180]

Hello

I am looking at donor bikes for a project for my partner (a long saga that many of you have helped with). I have found a decent option for a donor bike, A Specialized Vita in good condition and decent components but not too good. The issue is that it has V Brakes. I am an amateur bike mechanic and so know that good V brakes (and pads) can be as good as average Disc brakes BUT I also know that it does increase rim wear. On an unassisted bike this takes a long time but on a heavy rear hub motor and the extra weight of the battery as well how much sooner will I wear through the rim?

I am worried as obviously with a hub motor this would mean rim replacement and a wheel build, which isn't the end of the world but you don't want to be doing every year.

So what are people's experiences? Would you put a hub motor with V Brakes on and risk the wear?

Edit: it'll be a rear hub motor - Thanks Woosh.

 

[Woosh]

Unlikely. Most of the braking is done at the front and most hub motors are at the rear.
I have only ever seen one worn out rim in 11 years.

 

[Klang180]

Unlikely. Most of the braking is done at the front and most hub motors are at the rear.
I have only ever seen one worn out rim in 11 years.

Oh thanks for that perspective, coming from you that is very informative as I am sure you have seen a fair few bikes!

 

[Jodel]

The all up weight and the speed of the bike will be significant factors. When I was about 12 stone 7 pounds, it took me around 20,000 miles to wear through the front rim of my hard-tail MTB (on road use only) which was used in all weathers. It had cantilever brakes rather than V-brakes, but I'd expect the wear pattern to be similar.

I'm now around 10 stone 7 pounds, so even with the weight of a hub motor and battery, that is still a fair bit less than I used to be. For someone my weight and the sort of speeds at which I now travel, I'd be happy to use V-brakes on a 'suck it and see' basis.

 

[vfr400]

It's quite simple: 10% extra all-up weight means 10% more breaking is required and you get say 10% more wear.

On the other hand, if you increase your average speed from 10 mph to 12 mph and keep the weight the same, you need 44% more breaking, if you increase it to 15 mph, you need 225% more breaking, and 20 mph is 400%. That's the reason we recommend hydraulic disc brakes on any unrestricted bike.

To answer your question, rim wear is quite rare on legal electric bikes. There should be a wear indicator line on the rim. It's like a groove all the way round. When the groove has gone, it's time to replace. No need to panic or worry.

 

[Klang180]

The all up weight and the speed of the bike will be significant factors. When I was about 12 stone 7 pounds, it took me around 20,000 miles to wear through the front rim of my hard-tail MTB (on road use only) which was used in all weathers. It had cantilever brakes rather than V-brakes, but I'd expect the wear pattern to be similar.

I'm now around 10 stone 7 pounds, so even with the weight of a hub motor and battery, that is still a fair bit less than I used to be. For someone my weight and the sort of speeds at which I now travel, I'd be happy to use V-brakes on a 'suck it and see' basis.

Good point. My partner is 55kg, the battery probably around 4kg and the hub motor around 3-4kg I would say so let's say 65kg total. Still relatively light overall and should help reduce wear.

 

[Klang180]

It's quite simple: 10% extra all-up weight means 10% more breaking is required and you get say 10% more wear.

On the other hand, if you increase your average speed from 10 mph to 12 mph and keep the weight the same, you need 44% more breaking, if you increase it to 15 mph, you need 225% more breaking, and 20 mph is 400%. That's the reason we recommend hydraulic disc brakes on any unrestricted bike.

To answer your question, rim wear is quite rare on legal electric bikes. There should be a wear indicator line on the rim. It's like a groove all the way round. When the groove has gone, it's time to replace. No need to panic or worry.

Yes I personally follow that advice and have a bike with Hydros myself but then I am 87kg and have an unrestricted bike. I still much prefer the idea of her having hydro discs but that means more of an investment in the donor bike as well as less to choose from, something that is a bit of a pinch point at this time.

Thanks though, it is sound advice.

 

[Sturmey]

I tend to use the bike during the winter on wet and hilly roads, and the rear rims (and chain) tend to wear down quickly due to the spray of water containing road dust/grit from the front wheel. I use a mudflap on the mudguard but the rims still wear due to grit getting onto the rear rim and pads. The front wheel remains cleaner.
I think its mainly high mileage winter riders who complain of rim wear.
Anyhow, I am on my 3rd rim (i.e 2 rim replacements) with my rear hub with 22,000 km clocked up.

 

[georgehenry]

Before having an electric bike I loved leisure mountain biking and just before hydraulic disc brakes came in bought a very nice Marin hard tail with very powerful rim brakes and being a big bloke in a sandy area riding aggressively was getting through a set of rims a year.

After a few years of this a friend sold me quite cheaply some ceramic rimmed Mavic wheels at a good price second hand and they refused to wear out for the rest of the time I rode that bike.

 

[Artstu]

Where you ride and how quickly you ride is the biggest factor, I live and ride some very steep hills in the High Peak of the Peak District. I descend hills at over 50 mph at times for more perspective.
My rear rim on my new bike with hydraulic rim brakes wore out in around 8,000 miles, the front one is still going strong with several thousand more miles on.

 

[Klang180]

Thanks everyone. I think you have convinced me that disc brakes are probably the way to go. I think I will try and convince the BH that she is ok with a downtube and then we can get whatever bike we want (within reason!).

Thanks, all really useful info.

 

[KeithMac]

I do a rear rim in about 8,000 miles of commuting (plenty of stopping), that's in all weathers though.

 

[tonyw]

The biggest factor isn't weight or speed, it's how clean the rims/pads are. If you ride a lot in wet/gritty conditions, and you don't keep the rims clean you can wear out rims pretty quickly, in clean/dry conditions they might last 10x longer. It's worth buying good quality pads too like koolstop, some pads are quite abrasive.

 

[Raboa]

Isopropyl alcohol is good for cleaning rims and disk brakes, I put some on a bit of kitchen towel and give them a quick wipe. Isopropyl alcohol smells so better to do it outside if possible.