Another MTB --> commuter conversion. Questions

Ugo51

Retro Guru
Hi all,

I've seen plenty of similar discussions, I'm definitely not the only one using a MTB for commuting.
However...I'm having some issues adapting the bike to me and myself to the bike.

The bike is a 1996 Marin Bear Valley, I think 20' or 21' frame.
I am 170cm tall.

The issues I'm having is that, compared to a road bike, I feel like I cannot put enough strength on the pedals. I just can't push hard enough.
Maybe the frame is a bit too bike for me. I have the seat all forward and still the knee cap is a good 2cm behind the pedal axle.
Would that account for the difference in pedaling efficiency?

Thanks,

Ugo
 
It sounds a little big, but if you lack strength through the pedals, also check if the saddle is too low. With a straight leg and the pedal in line with the seat tube, your heel should be about 2cm below the pedal.
Marins also carried quite a lot of layback in the post, so an inline post may help.
 
Thanks.
I will double check the seat height again.
I had it a bit too high and lowering helped a little because it also moved the seat a little forward (as the tube is not vertical), but maybe I lowered it too much.

I was thinking inline seatpost or even one of those vintage seat clamps (like vintage road bikes) which I could fit in front of the seat post.


It's also very difficult to keep a high pedaling pace, if I try to spin the pedals faster...well, it just doesn't work. Possibly also a result of the incorrect seat position, both as height and fore-aft setting?
 
Re:

That's a very big frame for your height. I'm about the same height and for an MTB I would typically choose a 17 or 18" frame, 19" at most.
 
Re:

It is indeed.

Mind me, I might have gotten it wrong and maybe it's "only" a 20', but still...

Thing is that is such a nice bike. I thought it would have been easy to replace with another 90s MTB, but they are hard to come by at a reasonable price :shock:
 
It's it not just the sheer length of the up tube that's causing the issue?
You must almost be in a full Boardman Superman position.......
I'm taller (slightly) and even some of the longer/ more generously proportioned 18" are too big......
 
Re:

Not at all.
It helps that the previous owner fitted an horrendous extender, so the handlebar is actually too high for my liking.

So, the position itself is not bad. If I was to keep the bike I would in fact buy a top cap and bring down the handlebar slightly lower than the seat height.

But I've just tried the bike of a colleague, which is an even bigger frame than mine, and once I set the seat at the appropriate height, the KOPS was off of roughly the same amount than in my bike.
So the picture that emerges is that no matter what size I am riding my knees are always behind the spindle.
I do have shorter-than-average femurs, so that definitely doesn't help...
 
Doesn't help that KOPS is essentially a coincidence and has little or no relevance to bike sizing/ fitting.
;)
 
mattr":10y8hx1u said:
Doesn't help that KOPS is essentially a coincidence and has little or no relevance to bike sizing/ fitting.
;)

But in this case is useful to compare between bikes.
If the KOPS is off in any bike I ever tried (admittedly not many, I'd say 4), there is a pattern emerging :)

Cranks are standard 175mm.
 
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