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How to speed up MTB
#1
Hi!
Ok, I know topic name may sound confusing. My intention is to raise maximum speed of MTB while riding on flat ground. So, if I am giving my best I can go for example 45km/h. But, I want to raise that to lets say 55km/h.
Lets assume that all parts are new and clean.

Will upgrading cassette from 8 to 9 or 10 speed help? Does more speeds on cassette means more variations, or it means I will be able to go faster (with more power used of course)?

Is chain length one of factors too? Cranks?

Thanks!
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#2
To speed up a MTB for road use, the first thing to look at is your tires. Smoother, narrower, higher pressure tires will make you a lot faster.

As for gears, more gears doesn't mean more speed. It just means you'll have a finer adjustment between gears. What does matter is the size of your sprockets (how many teeth they have). If you have a really large front sprocket on a really small rear sprocket you'll be able to go faster. However, it would be hard to start pedaling from a standstill in that combination, which is why you have lower gears so you can work your way up.

Hope that helps!
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#3
I can't say that I can offer much more than experience on my own MTB and some knowledge of physics I picked up in my school days. But hopefully that will provide some ideas.

Probably the main problem that will keep you from more speed, all things being equal (namely your ability to put power into the bike), is friction. You can't do much about what the air produces (maybe wear tighter fitting clothes?), but you can do things about what the bike produces.

Perhaps the biggest one is the tires. Are they properly inflated? Low-inflated tires will cause more friction and lower the amount of energy put into the movement of the bike. Having everything along the drive train (wheels, chain, crank set, wheel bearings) properly lubed/greased will help too - as to reduce the friction between moving parts. But I assume that falls under your "all parts are new/clean" stipulation as well. I don't know if the wheel being out of true would be a factor, but it's a possibility.

Beyond that, you could look at what you are using the bike for. For my MTB, I don't go on dirt/mud trails with it - the worst is sand/gravel, and most of what I go on is blacktop. So I could think about switching out my MTB tires for road treads and gain an appreciable speed increase. In fact, my MTB with new treads is much harder to ride than the one with the treads wore down. The idea is, again, to lower the friction of the tires against the road surface.

Finally to the cassette. I don't know if you would gain a speed increase simply by switching them out for more gears. I have 7 speeds on the rear and don't notice much difference between gears 5 and 7. The way to get a speed increase concerns more the gear potentials (? don't know if that's the right word) between the front sprockets and the rear, and you would have to look at that. Decreasing the size of the rear and increasing the size of the front would gain more speed.

For example, switching my front gear into 3 gives me more speed with my rear gear in 5 than with the gears in 2 and 7. I would expect a similar change upon replacement of the cassette with the proper size (lower high gear, rear, higher high gear, front) - but again the question would come whether you would sacrifice anything in the lower gears for climbing hills. But that question of whether you could replace the cassette and gain anything is beyond my pay grade (for right now).

Hopefully some of that helps give you some ideas.
Why is it that they make adult bikes that'll generally work for 5'9" or above, yet when you pedal these same bikes they only work for someone who is 5'4" or so?
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#4
Thanks for your answer, sure it helps!

So, since most front chainrings are 44/32/22, is it possible to put on my bike some crank with only two chainrings, since they have more teeth (like 53/39)? I know they are made primary for road bikes, but how would it be to have that on MTB, and is it possible at all?

Can I use it in combination with MTB cassette?
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#5
Thank u very much Skguy for your answer too, u also gave me some nice ideas Smile

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#6
So, since most front chainrings are 44/32/22, is it possible to put on my bike some crank with only two chainrings, since they have more teeth (like 53/39)?

You can put a two chainring crank on, but you may run into issues with your existing bottom bracket and derailleur. It might be easier to just put some larger chainrings on your exisiting set-up.

Can I use it in combination with MTB cassette?

The new chainrings will work with your old cassette, but you might need to measure your chain as it may need to be extended. As chains/cassettes wear together this may mean you'll have to replace both.
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#7
Sheldon Brown has a gear/speed calculator
http://www.sheldonbrown.com/gears/

I switched from 26 x 1.95 knobbies to 26 x 1.5 slicks earlier this season and found I could push the bike @ 5 mph faster. My bike while MTB styled really doesn't qualify (strength-wise) as an MTB. I bought my bike for primarily road and some unpaved road riding. It came with the knobs but I knew eventually I would switch them out. I like the protection of not having the tire pressure too high, for the unpaved roads, and opt for around 45 PSI which seems to work for me. I guess I can get the bike up to about 20 MPH on flats but probably average in the mid teens speed-wise.
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#8
Hello, this topic is basically what I'm looking to do too. I currently have a 22/32/42 crankset and I'm planning on switching to a 28/38/48 crankset. I'm hoping this will give me the higher gears I need to increase my top speed. My question though is this: My current spindle length is 120mm and the crankset I'm interested in calls for a 122mm/122.5mm spindle. Will I have to change my bottom bracket or will the 2mm/2.5mm difference in my chainline be negligible?

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#9
It might work just fine with a 2mm/2.5mm difference. The main thing you want to watch for is that your chainrings don't rub on the rear chainstays when it is installed.

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#10
Glad I am not anyone thinking about it, hehe.

Anyway, I have spent last few days thinking about it, choosing parts, but the more I search I have more questions. So, thanks in advance Smile

I have decided I will change my crankset to 53/39. Currently I have installed 44/32/22. Doing that requires changing at least the front derailleur and chain. And since I will change chain, I will change the cassette too, and upgrade my rear derailleur and shifters.

So, many new parts needed. Requires some additional expenses, but I had to change old parts anyway.
I chose a 53/39 crankset which will fit my frame with no problems. Cassette will be Shimano LX 9 speed (I dont know if I am allowed to mention manufacturers and models here on forum, if no then please erase). Rear derailleur also Shimano LX.

So, basically speaking, on front I have road bike transmission, and on back MTB.

But now starts problems: Is it possible to do it? If i put some road-bike front derailleur for 2 chainrings, like Shimano Ultegra 6500, which is compatible to 9 speed cassette, what gear shifters to use?

If I use some MTB shifters, they are usually 3/9. I guess I can somehow adjust front shifter to change only two speed, but what concerns me: will I be able to shift gears on front with MTB shifter? Is road-bike shifter faster then MTB shifter?
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#11
You should be fine with MTB shifters, although your front shifter will have an extra click that does nothing.

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#12
Your MTB shifters should work fine although I think you will need to stay with the same number of gears in the back. Otherwise you may have trouble getting the indexing to line up properly. As stated above, more gears just means smaller increments between gears, not higher speed. Be very careful to set the limit screws on your deraileurs carefully after the change over to avoid chain falling off or worse (wheel/frame damage).

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