48yearoldN00b

I've got a GT mountain bike I bought used, that came with 26 X 2.125 tires, and the braking action was always very questionable.

The pads on the vee brakes looked ok, but the stopping action was very spongy. The front squealed whenever applied, and there was virtually no chance to clamp down hard enough to skid.

Recently changed tires and put in 26 X 1.995 tires on front and back...and the squealing on the front is totally gone, and the braking action on front and back is now superb.

I guess the previous tires might have been spreading the aluminum rims, causing the side profile to be slightly canted, reducing the surface area contacting the pad?

Surprised that .03" makes that much difference

Portis

not sure on that one.

mactheknife68

No chance. Possibly the tread grips better or your wheels were better centered when you reinstalled them but yer idea makes no sense.

Rev.Chuck

A fair amount of braking comes from tire grip. No matter how big a brake you put on a bike(or car/motorcycle) it will not stop quicker than the smallest one that will allow modulation up to lock up. The only way to improve braking is to increase traction. This changes as the brake gets hotter thru repeated braking, then bigger can be better.

48yearoldN00b

bad math on my part, the diff is .13"...but considering how poor my braking was, and the dramatic improvement after the tire change, I'm a tad in disbelief too.

Wasn't even expecting an improvement in braking, but I sure got one.

seely

I'm guessing the wheels were not seated properly in the dropouts, and upon reinstallation after the new tires they were seated properly.

Wil Davis

I wonder if in changing the tyres, you unknowingly cleaned the braking surfaces on the rims (or even the brake-blocks), or at least removed some of the crud which might have been causing the squealing?

- Wil

Stacey

My money is on #6.

willtsmith_nwi

Nothing to do with it.

Perhaps you spilled some solvent on the brake pads while you were changing tires. If anything, larger tires should actually make braking work as they increase the effective diameter of the wheel. This in turn causes the wheels to spin slower for a given linear speed. This translates to less heat generated by the pads which means less braking power.

Stacey

Somethings you just have to write off to F.M..

48yearoldN00b

>>I'm guessing the wheels were not seated properly in the dropouts, and upon reinstallation after the new tires they were seated properly.<<

well, I have had the wheels on and off several times over the year that i've owned the bike, putting it into the trunk of my car. And I did nothing differently about re assembing the bike this time

Little Darwin

If a different tire width is making a difference in your rims angle at whatever pressure you are using, go get some new rims.

I have put slicks on my bike with 26" rims and have always inflated to the max the tire would take (now 85 psi) and have never had them make a difference in brake squeal of functionality.

48yearoldN00b

>> wonder if in changing the tyres, you unknowingly cleaned the braking surfaces on the rims (or even the brake-blocks), or at least removed some of the crud which might have been causing the squealing?<<

That is a good guess, but I had already tried on numerous ocassions to clean the pads, rims, etc trying to improve the obviously substandard braking.

I even wiped the rims down with solvent and buffed vigorously LAST SUMMER ...to no avail. even brushed and wiped down the pads, to no avail.

Now, I gotta be carefull laying on the front brake too heavy, because the stopping action is so effective.

Before the change, the stopping was BARELY acceptable. And by acceptable I mean that since nothing I was trying to fix it seemed to be working, I was left no choice to accept what I got.

In comparison, the braking action is almost awe inspiring now,

48yearoldN00b

>>My money is on #6.<<



sorry, but not very likely

48yearoldN00b

except that I was using no such solvent or fluid when changing the tires

And, because the brakes were troublesome last year, I tried several different things trying to "fix" my brake problem,..(back then) all to no avail.

That's why I am so counfounded by the dramatic improvement that seems to have resulted from an unexpected source.

Hey, I may not be a "sheldon brown" but I have a fairly adept mechanical aptitude, working with boilers, chillers, pumps, belt drives, and the sort for over 30 years.

And looking at what happened is more of a surprise than anything else

48yearoldN00b

[QUOTE=Little Darwin]If a different tire width is making a difference in your rims angle at whatever pressure you are using, go get some new rims.

[QUOTE]\

why? the 'problem' was with the previous tire set up. everything seems fine now. I'd hate to go out and get new rims, and have the squealing come back.

Bill Kapaun

The newer tire has less weight, so there is less rotational mass to stop.
The older tire was a larger diameter, so it has more "leverage" vs the brake pad.
It MIGHT have also had better traction.
I'm not sure if that combination is enough to make a difference by itself. Maybe with both tires??

However, just because the tire skids doesn't mean you are stopping faster. Maximum braking occurs just before the tire skids.
Could be when changing the tire, you knocked the brake pad SLIGHTLY and now hits the rim a BIT differently. If your "old" braking returns as the pad wears, that may be it. Maybe a combination of all of the above.

TimJ

Of all the maybes I think one can be absolutely sure your tires were not spreading the lips of your rims out.

CaptainCool

Even if this were the case, the pads would quickly rotate or wear down to match the angle, and so braking should be worse for a while upon changing tires.

Tread differences would affect the ability to skid. Not being able to skid can be a good thing - skidding is never the fastest way to stop, as far as the tires are concerned. I wouldn't think the weight would matter that much on a mountain bike.

Bill Kapaun

"I wouldn't think the weight would matter that much on a mountain bike."

When I went to a skinnier "street" tire on the front, the improved acceleration was VERY noticeable when sprinting across intersections after being stopped at the light. Conversely?, stopping should be improved for the same reason. LESS WEIGHT!

48yearoldN00b

Perhaps the most noticeable attribute of the improved braking is thecompression on my wrists as the bike slowsdown more deliberately, leaving the weight of my body to "inertia" into the handlebars.

The first time I really layed into the brakes, the stopping action was so vastly improved over what i had been used to, that my body inertia against the handlebars spun the complete handlebar assembly forward 90 degrees, and I almost wiped out.

I weigh 250 lbs, and for a while I expected that all my weight was what was keeping the brakes from working satisfactorialy, so much weight that the tires would not skid, nor could the brake pads hold back the inertia.

But that theory went out the window with the first trial after the new tires.

You guys realize that an inflated innertube exerts a lot of force over it's entire surface area.

If you put an old auto innertube laying flat under a car, and inflate it, you can actually lift the car off the axel on that corner of the car.

Eatadonut

Tighten your stem.


are your brakes touching your tires? had to ask.

mycoatl

Maybe the OP went from knobbies to slicks. That would certainly explain the difference in braking.

Eatadonut

No, it wouldn't. He said it stopped squealing and his brakes clamped hard enough to skid. That's not at all related to the tires, with the exception of skid power.

Any chance you knocked the brake pads into/out of alignment in the process of removing and installing the wheel?

Barabaika

Squealing is usually comes from small metal particles from the rims that punched the brake pads and stay there. You should open the brakes, take the first wooden twig from the ground, and clean the pads.

Also, in the auto world there are different tires with different stopping power. Slicks are the best because the rubber is very soft, but their life is very short - 12000 miles.