Need some assistance !

[PloddingAlong]

Hi everyone,

New to the forum, i'm really at my wits end trying to find information so I thought i'd try here

Anyway, I have a couple of questions that I cannot find answers too.

I am a pure casual cycler, I do it to keep a bit fit as I suffer with my health, and it's proven something I really enjoy.

I purchased a Trek 7.0 FX Hybrid a while back, and it's been great, I love the bike, so much fun to use.

I have a couple of problems now with wear and tear. Basically I need replacement brake pads, for the rear and I probably should do the front too, so what ones should I be looking for ? I cannot find various spec's on Trek's site for sizes or recommendations etc. So any help here would be appreciated.

Also, the front derailleur is almost spot on, I adjusted it not so long ago, and it's been ideal so far, but it sometimes refuses to drop from middle cog to smallest cog under load ! The limits are set fine when it's in the garage, but it seems to be a lot diferent under load.

You think I need to re-adjust the lot again ? It's great when on the flat not being taxed, but going uphill it sometimes refuses to drop down.

Thanks for any help, I really appreciate it.

 

[PloddingAlong]

OK so from the research i've done, they are Vee Brakes and the pads are just standard Vee Brake ones, but when I looked there are different sizes, so does it matter what size I get ? Are there better brake pad materials than others or shouldn't I worry about that and get standard ones ?

 

[Volnix]

Hi! /img/vbsmilies/smilies/smile.gif

Brakes are a very very complicated mechanism. Brakes change the kinetic energy of the wheel (movement) into heat with the friction between them and the wheel. Bigger brake pads would probably absorb more heat (not very sure about the heat absorbing limit but thats why disk brakes get glowing red hot I think). A brake pad with a bigger surface would probably produce more friction as well since there is a bigger contact area between the brake and the wheel. Some disk brakes now have 2 or more pistons which apply to the disk surface for the same reason I suppose. The compound of the pads is another story. There are probably several compounds for different kind of uses. I would go for one that is very friendly to the wheel, work well on rain etc and brakes very well too. Brake pads are usually cheap I think (unless you get some very weird stuff) so being a bit easy to wear out doesnt make much of a problem maybe.

Since there is no friction between the chain and the derailur when the gear is changed I would say that the derailur is probably adjusted in the correct position. But if the chain doesnt move when the derailur is pulling it to the correct position its might be an issue with the tension? of the chain? Maybe if the rear wheel was moved a bit further back then the chain would have less "play"? and it would move to the correct position,not really sure about this, just an assumption.

 

[PloddingAlong]

Hi, thanks for your replies.

Can I use a longer brake pad with my bike or do I need to stick to the size that's there now ?

As for the chain, i'll make sure the tension isn't too great, and recheck the cable tension too.

Thanks again.

 

[dabac]

For V-brakes there's only one type of mounting method(cantis have two), so there shouldn't be any trouble.
And yes, you can use different lengths. Differences in brake pad material will be far more important than differences in length.
Remember that the front end of the pad should touch the rim first, or you can expect brake squeal.
Brake pads come in different compounds depending on type of rim(alloy, ceramic, Carbon fiber), and to a lesser degree, riding conditions. It's quite important to match your rim type.
If you're wearing out your rear brake first, you probably could do with some brake technique training. Pretty much the only time heavy use of the rear brake is "OK" is under very slippery conditions.

For front shifting, don't expect too much. Front shifting happens on the tensioned side of the chain, so if you're putting plenty of pressure on the pedals,the derailer won't shift - end of story.
Easing up on the pedals while shifting at the front is likely to yield far better results than tinkering with the derailer/shifter.

 

[PloddingAlong]

Hi, thanks for the advice, i'll look into my braking technique, the rear has worn down a lot quicker than the front, the front is fine to be honest.

I'll also be ordering some brake pads, at least now I realise that the length isn't too important, the same or slightly longer will be ok.

I guess I should scout about for what suits the rims better and what other people use. I hear that aztec and avid are good ones to use, although I have no experience with them.

Thanks again.

 

[dabac]

Originally Posted by PloddingAlong .

Hi, thanks for the advice, i'll look into my braking technique, the rear has worn down a lot quicker than the front, the front is fine to be honest.

Here's some suggested reading on brake technique:http://sheldonbrown.com/brakturn.html

 

[PloddingAlong]

Excellent , thanks for that, seems I am more back brake happy, I tend to use both a lot as loads of downhills.

Thanks for all the advice, can carry on cycling a bit more informed now

 

[okhealthy]

I first came to this, See a lot of point of view, Very much .

 

[maydog]

Your front chainring shifting could be affected my a gummed up cable or derailleur that doesn't pull like it used to. On an old bike of mine, I need to give the derailleur a little "kick" to get to the smallest cog.

With the bike on the bench / or stand - check to see how quickly and fully the derailleur moves to the lowest position. If it is slow or doesn't go all the way - something may be due to a cleaning, lube and/or service.

 

[PloddingAlong]

When I check it in the garage, it seems to shift fine, and the chain jumps nicely up and down. It's OK when i'm out on it, but the slightest load and it seems to stop shifting so well. I readjusted the derailleur the other day, havent had a chance to get out and test it yet under load. Fingers crossed

 

[davereo]

DBAC was spot on with the shifting under load being the issue. You can try down shifting in the rear to a lower gear before shifting to your lowest in the front. This may help a little into getting your front to shift over.

Also if you pick up your pedaling cadance a little and shift earlier you will find the shifting much improved. Like your braking you may have to work a little on your shifting technique. Its best to shift ealier when you know you will be approaching a point on the climb that you need a little help from your gearing.

 

[davereo]

Another thing for you to keep in mind is the front deraileurs movement towards the smaller chain rings is controlled by spring tension only. The spring in your deraileur is not strong enough to overcome the chain being wrapped firmly around the chain ring. Shifting upwards is done by the cable being pulled by the force applied on the shifter that is why you are only having this problem downshifting. So with this in mind nothing is wrong with your bike.

 

[maydog]

davereo is correct, I semiconciously, briefly, let up on the pedal force when downshifting chainrings. I bet many others do to.

 

[PloddingAlong]

Thanks guys, much appreciated, i've done that now, I pedal a bit harder into the hill to build up a bit of momentum, and she changes down perfectly. It was the load doing it, and as you say, not enough tension to pull the chain down one. Excellent advice, thanks.

I just fitted the brake pads, not tested them yet, they are longer slightly than the old ones, does that matter ? They fit the rims ok, so I assume not.