Shortening effective top tube length with 120mm fork

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HamboCairns

Thanks for all the bananas
Hi all,

My wife has been suffering a little lower back pain riding her bike recently.

She rides a Trek Marlin and chose it because no women specific models were available at the time and it seemed to fit ok at the time.

I'm thinking that she's stretching just a little and thought reducing the top tube length would be in order by way of acquiring a 120mm fork and a much shorter stem. She'll have a more capable trail basher at the same time!

What do you think? Make sense?

Also this is a long winded way of asking if anyone has a 120mm air fork with 1-1/8 straight steerer, 9mm QR and a 51mm offset lying around...

I'm not fully committed to this yet hence posting here rather than the WTB section.

Thanks all!
 
S

schred

Likes Bikes and Dirt
Because it shall raise the bar height whilst pivoting around the rear axle by the cosinetangent of the moon, ie. rearwards by a bees dick.

If the intent was to reduce ETT & reach to the bar, I'd think better to shorten stem, sweep bars or even slide saddle forward if her knees will tolerate it, also make sure bars aren't too wide pulling her forwards.

In saying that, lower back pain can come from heaps of things, heaps. I'd also try free things first - shift the saddle forward which also opens up hip flexors, get as much weight off her back as you can, get her to stretch her hip flexors and thigh muscles regularly incl before and after rides and try not to hunch over the bars too much, maybe even slide the controls inboard a few cm if the bars & terrain allow for it.
 
The Duckmeister

The Duckmeister

Has a juicy midrange
schred said:
Because it shall raise the bar height whilst pivoting around the rear axle by the cosinetangent of the moon, ie. rearwards by a bees dick.
Click to expand...
All pivoting around the rear axle will do is change the tilt of the bike. All the cockpit points are in exactly the same position relative to each other. 'Cos you might be lifting & pulling the bar back a poofteenth, but remember the saddle is also fixed to the frame, so that's going to effectively come back too.
 
S

schred

Likes Bikes and Dirt
This is true, but relative to each other is in a rotating frame of reference, which is different to relative to horizontal ground which is what is counts. Rotate enough and the ETT becomes zero, woot.
 
The Duckmeister

The Duckmeister

Has a juicy midrange
But with one hell of a handlebar rise....

The kind of change being contemplated will do exactly fuck-all to the ETT.
 
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HamboCairns

Thanks for all the bananas
I thought that a lower rise and shorter stem as well as moving the saddle forward would complete the package.

But I can try the shorter stem route first, I don't think we're that far off. My wife does yoga so she's relatively flexible, it's just the stretched out position that's annoying.
 
moorey

moorey

call me Mia
HamboCairns said:
I thought that a lower rise and shorter stem as well as moving the saddle forward would complete the package.

But I can try the shorter stem route first, I don't think we're that far off. My wife does yoga so she's relatively flexible, it's just the stretched out position that's annoying.
Click to expand...
Shorten stem, move seat forward.....120mm forks by all means, but they won't do anything.
 
pink poodle

pink poodle

気が狂っている男
There is a better method that is often overlooked. Loosen her stem, rotate it 180deg, tighten stem. If this isn't perfect try a longer/shorter stem to suit. You way also want to consider a rise in the bars or stem.
 
spikenet

spikenet

Likes Dirt
Maybe try a bit of physical conditioning, if your not used to riding allot then no matter how you setup your bike you will get some soreness in the lower back. My wife just started riding and had similar complaints, Pilate's is great for core strengthening..

Sent from my Nexus 5X using Tapatalk
 
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