Setting Up Wheel With Brakes

willowen100

Hi guys

I have a 2015 Marin Bobcat Trail 7.4 https://www.marinbikes.com/gb/bike-arch ... -trail-7-4 bike and it's lovely to ride, however since day one of owning it I have never been satisfied with the performance of the brakes compared to V-brakes I had on my previous bike. To explain how poor the brakes are you could say slamming the brakes down on a 25% gradient hill on the road should have locked the wheel and made skid marks, maybe even thrown me over the handlebars.

After trying every fix in the book to strengthen my brakes up ;doing two brake re-bleeds per wheel, lightly sand papering the brakes down, using brake cleaner and aligning the calipers, I have now decided to buy some new pads to eliminate contamination of the brake pads. I was initially thinking of blowtorching the brake pads, but couldn't justify the time and effort compared to buying a new set.

Even with the brakes not performing the way I wanted them, my front wheel has always scraped the pads slightly on the one side. This is what lead me to realigning the calipers. However, one of the pistons doesn't full retract and I would say it sticks out by 2-3mm. I have tried using a spanner end to push the caliper back in but it only affects the one piston, and the problematic one eventually seeps back out to 2-3mm so never stays in place once the brake lever is applied a few times. Additionally whilst I had my hand on the front wheel to spin it around, I noticed it was rocking when I pulled on it from the sides. Somehow the wheel axle had come loose. What I would like to ask is, does the wheel axle need to have equal spacing either side of the wheel, and would this have an affect on the alignment of the brakes?

Hope someone can help me out here please.

Many thanks

Will

cooldad

The axle will make no difference as the calipers attache to the hub. As long as there's enough axle in the dropouts.

Was the bike second hand?

And assume you bled with mineral oil and not DOT fluid?

willowen100

cooldad wrote:

The axle will make no difference as the calipers attache to the hub. As long as there's enough axle in the dropouts.

Was the bike second hand?

And assume you bled with mineral oil and not DOT fluid?

No the bike was brand new. I used a different colour mineral oil so I could see the old oil being drained out.

larkim

The wheel rocking sounds like an issue in itself surely, but may not be related to your brake issues.

Uneven spread of pistons isn't unusual, nor is a very small amount of catching if one piston doesn't retract as readily as the other. I've not done it, but cleaning the pistons might allow for a more even position, but it could well just end up with the same situation you're in now.

If you've got contaminated pads, you could have contaminated discs too, so new pads might not solve the issue either. Can you rotate the wheel by hand whilst the brakes are fully applied?

steve_sordy

willowen100 wrote:

cooldad wrote:

..................
And assume you bled with mineral oil and not DOT fluid?

No the bike was brand new. I used a different colour mineral oil so I could see the old oil being drained out.

But did you use the correct oil? :?:

willowen100

steve_sordy wrote:

willowen100 wrote:

cooldad wrote:

..................
And assume you bled with mineral oil and not DOT fluid?

No the bike was brand new. I used a different colour mineral oil so I could see the old oil being drained out.

But did you use the correct oil? :?:

Yes. I have Tecktro brakes and they use mineral oil. I'm no hydraulic brake expert but what exactly is behind the pistons? If I take them out completely is the brake fluid going to leak out or is there something else behind it. I've seen a video of someone pulling the brake the lever to release the pistons and then applying silicon grease to them. However, would there be any need to fully remove the pistons to maybe full grease them?

As a side the note the brake rotor isn't bent and the wheel axle has been tightened up. I think if I can get the one piston to retract back in like the other one I can then align the caliper and everything will be sorted in terms of noise and uneven wear.

On my old pads I actually remember being able to fully depress the lever and with some force I could move the bike forward. I have not tested this yet with the new pads as setting the spacing on the pads equally was more of a priority.

Many thanks

Will

Tetragrammaton1

The oil is probably the key to this one. Mineral oil for your brakes, also you could try changing compounds of the pads.

cooldad

willowen100 wrote:

...
Yes. I have Tecktro brakes and they use mineral oil. I'm no hydraulic brake expert but what exactly is behind the pistons? If I take them out completely is the brake fluid going to leak out or is there something else behind it. I've seen a video of someone pulling the brake the lever to release the pistons and then applying silicon grease to them. However, would there be any need to fully remove the pistons to maybe full grease them?

If you remove them, the fluid will not leak out, it will just pour out, so don't do it. And don't use grease to lube.

If they are sticky, you can use a little mineral oil on an ear bud or something, working them in and out a bit, but make sure you don't pop them all the way out.

Shouldn't need to though.