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[Closed] Rear brake lever feeling more spongy than the front one

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[#5662110]

Is it very common that the the rear brake lever always feels slightly spongy than the front one, due to longer hose? Assume everything is perfect, e.g. no air bubble trapped, fresh fluid, perfectly aligned calliper, no lazy piston, true rotors...etc

I am currently using Hope Tech EVO M4. Today, I got a fresh new bleed (both F/R) from LBS and it feels like mentioned above, even in day one, the date I purchased them brand new from Hope.

Any thoughts?


 
Posted : 04/11/2013 3:34 pm
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It's *possible* that the hose expands slightly under pressure and thus a longer hose will expand slightly more than a shorter one. Certainly on my car changing to braided hose over standard ones firmed the whole braking system up but I don;t know if pressures in mtb systems are enough for this to be an issue.

I suspect it's still likely that there is air somewhere causing this - I manage to get both my brakes with the same feel post a bleed, anyway.


 
Posted : 04/11/2013 3:38 pm
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@wwaswas

What brakes are you using? Also Hope ones?


 
Posted : 04/11/2013 3:44 pm
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I have been wondering this recently. I have bled both my SLX and XT brakes and the front ones are great. But both back ones are not quite as sharp. I tried bleeding them again and still can't get them as good as the front.

Given up now, just riding them as they are.


 
Posted : 04/11/2013 3:55 pm
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My XTs have always been slightly spongier on the back despite numerous bleedings.

On my old Hope Minis, changing the rear hose made it far more positive.


 
Posted : 04/11/2013 4:08 pm
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[i]What brakes are you using? Also Hope ones? [/i]

Mine are all Maguras- I think I was trying to argue against hose expansion being the issue, really - at least for me.


 
Posted : 04/11/2013 4:10 pm
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My XTs have always been slightly spongier on the back despite numerous bleedings.

Same here. I even got my LBS to bleed then in case I was doing it wrong and it was the same.

I just accepted it as a fact of life!


 
Posted : 04/11/2013 4:14 pm
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Iv always noticed this with hope brakes - apart from my braded V2's. So probably hoses flexing as stated


 
Posted : 04/11/2013 4:15 pm
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Is it very common that the the rear brake lever always feels slightly spongy than the front one, due to longer hose?
yes


 
Posted : 04/11/2013 4:17 pm
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I tried to think of it with some basic physics.

Both lever (Front and Rear ones) are identical which generate the same amount of force to push the fluid in each hoses. The longer hose (rear one) must contain more of it. So the forces that end up at the pistons will be weaken.

Longer hose allows more extension in the hose under pressure.

Longer hose results in more resistance? Just like electric cable?

I am just trying convince myself that the defect of the rear lever is NORMAL. ๐Ÿ˜‰


 
Posted : 04/11/2013 4:21 pm
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TJ Im sure denied this was the case. I beg to differ though and suggest the hose does expend more due to it length. Expansion can probably be lessened further by changing to a braided hose.
But in both my bikes, the rear does feel slightly spongier. (same hoses, calipers, levers etc for front and rear)


 
Posted : 04/11/2013 4:54 pm
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And this is why I like my braided hoses. Both brakes pretty much the same, makes modulating a bit more intuitive.


 
Posted : 04/11/2013 5:07 pm
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I was about to start a similar thread... both levers feel about the same but the performance of the rear always feels poor compared to the front.

I'm wondering if it's partly due to the disc / pads being contaminated with oil / lube from the drivetrain?


 
Posted : 04/11/2013 5:45 pm
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Are Hope standard hoses still unbraided? I can't say as I can feel any difference between front and rear on any of mine but Formula hoses are kevlar braids as standard I think.


 
Posted : 04/11/2013 5:52 pm
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just noticed that my front one is a bit slower to return than the back too..... 6 month old xt's, not likely to be needing bled....wonder why ? (it is only 4 deg in my garage, which may may the fluid a bit sluggish I guess ?


 
Posted : 05/11/2013 5:49 pm