frame alterations

M

manny24

Likes Bikes and Dirt
anyone here ever had there chainstays\ seatstays reduced in length in order to improve there frames feel\performance??
im thinking mainly cro-mo, but alloy too i guess. the most obvious fromes would be the dabombs, maybe even the dmrs.

(yeah, i know. this question screams of 'Grip' :wink: )
 
CHEWY

CHEWY

Eats Squid
A simple way I've been thinking about doing it is to extend the horizontal dropout slots on my DMR. Could get close to shortening the stays by about 1/2 an inch doing it like that, which would get them to 16".
But then there would be a lot less meat left in the drop outs, I'd rather just live with it as it doesnt worry me much at all.
 
wombat

wombat

Lives in a hole
IMO, unless you've got a frame that is in perfect in every other way, it's almost a bit of a waste of time (yes, Jon is going to slap me for that :p ).
If you have horizontal dropouts like Chewy mentioned then it may be worthwhile doing, but the big thing you have to take into consideration is tyre clearance.
Frames with super short stays will usually use some funky yokes or tubing manipulation to achieve adequate tyre clearence when the tyre is so close to the BB. If you're just looking at hacking into your d/o's, you'd want to make sure you had plenty of room to play with at the other end of the stay.
Of course, if you want to completely remove the stays to shorten them, then you could put in a high clearence yoke anyway, but personally I question the value of carrying out such major changes to a frame as it may well be more practical just to buy one that is right in the first place (or get a custom frame made from scratch).

Really though, this is just speculative dribbling, so ignore me and wait for Grip. :)
 
J

jays_5000

Likes Bikes and Dirt
I have never heard of that happening before, but a guy has cut his stays in two peices and welded a flat bit of metal in the gap so as he could fit 3" tires (Kona stuff). I wouldn't trust it, tubing snaps easy enough let alone a flat bit of metal sheeting.
 
Grip

Grip

Yeah, yeah... blah, blah.
I think Chewy's idea is the most workable. We've done a few of them, including Ryan's DMR that we opened up from this

to this

but you really need to then gusset the chain/seat stay joint (at the dropout).

Wombat is also correct about tyre clearance and yolks etc. and a lot of frames just wont let this happen easily.

But the biggest problem of the lot though, really, is the fact that you would probably have to alter the angle of the seat stays in order to get them to re-connect with the now-shortened chain stays. And that all adds up to basically replacing the entire rear triangle... which is possible so long as you don't mind some decent gussetting such as these before and after shots


And really if you weren't prepared to gusset the hell out of it you would be asking for it to fall apart pretty quick. So if you can find the ideal rear triangle it can be done by doing a cut & shut....

.... Or an easier way (if the frame will allow it for tyre clearance) might be to replace the dropouts (horizontal) with ones that are slotted enough to allow placement of the wheel further forward and where you want it. That way there's no great drastic changes.
 
M

manny24

Likes Bikes and Dirt
wow, some interesting work! ^^^

what i was thinking tho, was to cut at the b\b and seattube area, remove appropriate length, then reweld etc. this would prevent any problems with tire clearence, or rim brake posts positioning etc ( i was thinking more of vertical dropout frames here)
i can forsee a problem with chainline tho, what with the RH chainstay being closer to the crank spider. but i figure running a single ring up front on the outer mount would solve this.
 
R

Ryan

Radministrator
Just for reference, the work Grip did on my DMR shortened the chainstays from about 16.5" down to spot on 16", which kicks serious arse and solves one of the only problems I had with the frame :)

If you've already got horizontal dropouts, I say go for it, you've got nothing to lose (except inches of wheelbase / chainstay length) and plenty to gain, the .5" difference in chainstay length has made a real, positive difference to the way the frame rides.
 
wombat

wombat

Lives in a hole
manny24 said:
wow, some interesting work! ^^^

what i was thinking tho, was to cut at the b\b and seattube area, remove appropriate length, then reweld etc. this would prevent any problems with tire clearence, or rim brake posts positioning etc ( i was thinking more of vertical dropout frames here)
i can forsee a problem with chainline tho, what with the RH chainstay being closer to the crank spider. but i figure running a single ring up front on the outer mount would solve this.
Click to expand...
I think crank clearence may just be a bigger issue than you imagine. Aside from that, I don't see how cutting the seat tube and sliding everything forward is going to make any difference to the stay length, so I'll assume you cutting the stays at the BB junction.
In that case, were you planning on ignoring the change in seat stay angle, or cutting and altering them too?
 
M

manny24

Likes Bikes and Dirt
manny24 said:
what i was thinking tho, was to cut at the b\b and seattube area, remove appropriate length, then reweld etc. this would prevent any problems with tire clearence, or rim brake posts positioning etc ( i was thinking more of vertical dropout frames here)
Click to expand...
thats the idea, yep. tho iwas probably not clear on it eh
 
Grip

Grip

Yeah, yeah... blah, blah.
Have you got the frame you want to do this too yet? If so post a pic of the dropouts from side on. You MAY be able to modify the dropouts themselves in such a way that you create a NEW axle position further forward. Obviously no good if moving the wheel itself is impossibe because of clearance, but if it IS possible then it would save a lot of rebuilding work.
 
Grip

Grip

Yeah, yeah... blah, blah.
The Grenade would be pretty perfect for the dropout modification I was thinking of. Looks to me like there'd be plenty of room to move the whole axle point forward about 20mm at least. You'd have to re-fit the disc mount (no big problem) and MAYBE remove the chain stay bridge, pinch the inside of the stays for extra required tyre clearance and then fit a gusset like this UNDER the B/B and chainstay joint to replace the strength lost by removing the bridge.



Like I've always said... everything is possible... some things just take more time and cost more.
 
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