Sprint 7 Rear Brakes

Jeanette Morgan

Pedelecer
Nov 29, 2006
114
0
CORNWALL
I think my rear brakes are not working properly - how should I adjust them ? When ridinng if I pull the rear brake handle nothing seems to happen, the front ones are effective and I can stop - however, the strange thing is that when stationary if I pull up the back brake the bike seems to be effective and I have to release the brake to push the bike.

Thanks for your help, as always.
 

Ian

Esteemed Pedelecer
Apr 1, 2007
1,333
0
Leicester LE4, UK.
Hello Jeanette,
I presume you have the Shimano roller brake normally fitted to the Sprint. If when applying the brake the lever reaches the limit of travel before contacting the rubber handlebar grip then the brake does not need adjusting. This kind of brake is not particularly powerful and does need a lot of pressure to be effective. You can test the brake by applying it hard while riding at walking pace or a bit faster, the rear wheel should lock and slide along. If it passes that test then it is probably working OK, just needing more pressure than you perhaps normally apply. The rear brake will always seem weak when compared to the front, but particularly so in the case of the Sprint and similar bikes which use a different brake on the rear. The advantage of that type of brake is that,. unlike the front brake, it needs virtually no adjustment or maintenance which makes it unlikely there is actually anything wrong with it.

Ian
 

flecc

Member
Oct 25, 2006
52,763
30,349
Further to Ian's answer which is what I find on these brakes as well, the design limit of that Shimano roller brake is 100 kilos for bike and rider.

On an electric bike, it's weight uses up a much higher proportion of that than on a normal bike, and if you add the Sprint's 29 kilos to your own weight, you'll see that you're in the upper half of the range, and therefore it's at the weaker end of the brake's effectiveness.

The main advantage of this type of brake, as well as the low maintenance that Ian has mentioned, is the avoidance of the rim wear that pads cause. That makes it ideal for the routine slowing down, retaining the front rim brake for when more braking power is suddenly needed.
.
 

Jeanette Morgan

Pedelecer
Nov 29, 2006
114
0
CORNWALL
Just thought I'd let you know my rear brakes are fine - I discovered this when the bike was on its stand and I was oiling my chain. I spun the pedals and the back wheel was going fast - I applied the brake and it stopped immediately.

I also found that a better understanding of the back and front brake has helped with my suddering problem, I've found that if I don't use the back break once I've almost stopped, resorting to the front only, I don't get the suddering quite so much.

Thanks for your help and advice, as always.
Jeanette
 

slimtim

Pedelecer
Jun 6, 2007
32
0
Birmingham
damsel in distress

the design limit of that Shimano roller brake is 100 kilos for bike and rider... if you add the Sprint's 29 kilos to your own weight, you'll see that you're in the upper half of the range...........
.
this is no way to treat a lady!!:cool:
 

flecc

Member
Oct 25, 2006
52,763
30,349
Ah but I chose my words very carefully Tim, not saying the word weight, and leaving Jeanettes contribution as little as 22 kilos by my use of "the upper half"! :p

Anyway, I'm sure Jeanette knows my replies to her well enough by now to know that I'd never be ungallante. :)
 

ITSPETEINIT

Esteemed Pedelecer
Dec 11, 2006
492
0
Mere, Wilts
I need liposuction

Further to Ian's answer which is what I find on these brakes as well, the design limit of that Shimano roller brake is 100 kilos for bike and rider.

On an electric bike, it's weight uses up a much higher proportion of that than on a normal bike, and if you add the Sprint's 29 kilos to your own weight, you'll see that you're in the upper half of the range, and therefore it's at the weaker end of the brake's effectiveness.

The main advantage of this type of brake, as well as the low maintenance that Ian has mentioned, is the avoidance of the rim wear that pads cause. That makes it ideal for the routine slowing down, retaining the front rim brake for when more braking power is suddenly needed.
.
That's not good news Flecc. Can they be serious? Are these bikes for lightweights.
I'm 6 ft 3 ins, 200 lbs (91 kgs) + bike (29 kgs) + shopping or luggage (13.6) kgs and spare battery (5kg) = 138.6 kg.
I'd better buy an anchor to throw out.
My wife also exceeds that limit under similar circumstantial load = 108.6 kgs.
But seriously, I've never noticed any problem stopping. I got a bit of brake fade going down hill once and the front brake made a noise like a banshee.
Peter
PS what about the build of the rear wheel under these conditions - advice would be useful.
 
Last edited:

redalpha3

Pedelecer
Oct 31, 2006
91
0
That's not good news Flecc. Can they be serious? Are these bikes for lightweights.
I'm 6 ft 3 ins, 200 lbs (91 kgs) + bike (29 kgs) + shopping or luggage (13.6) kgs and spare battery (5kg) = 138.6 kg.
I'd better buy an anchor to throw out.
.
I think you'd better put me down for an anchor too. Maybe we could get a job lot?:D
 

flecc

Member
Oct 25, 2006
52,763
30,349
I must admit that I haven't had a problem with the roller brake, just using it for all routine slowing and the front for the odd occasion when more is needed.

I've only changed it now as part of other mods which made it necessary.

As for the rating of that brake, it's the old problem of cycle parts just being designed for cycles, not for electric bikes. There's exactly the same problem with hub gears that Giant experienced with the crank drive series, under motor plus rider power, they could sometimes fail, being only designed for rider power.
.
 

Jeanette Morgan

Pedelecer
Nov 29, 2006
114
0
CORNWALL
Flecc,

You are, indeed, most gellante!!

It was interesting to learn about the rear brake - I'm an "average" sized 5'5", well perhaps slightly over, but I do have a back box fitted on my bike which is oftentimes full ! I always put the heavier items there, rather than in my front basket - so there is a fair bit of weight on the back wheel, my shopping, like myself, differs from time to time ! I'm happy to have tested the brake the way I did and am now concentrating on using both braking systems as they should be used.

Kind regards
Jeanette