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Old 08-18-11, 04:47 PM   #1
Eddie50
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Could rear spacing be reduced from 145mm to 130mm? If so, how?

I have a project to build a Time Trial and Triathlon tandem from a Cdale or trek frame, but want to use single bike wheels for better availability in case of flats and for more choices in aero wheels.

I know that its not a good idea and not recommended, but remember, it will be a dedicated TT bike.

sooo, is it possible with alu frames like the cdale or trek?
or is there a way to frabricate adaptors that will not require messing with the frame?

Thank you
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Old 08-18-11, 05:02 PM   #2
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Not an expert on this but I don't believe you will be able to change the dropout spacing on an Al frame. You might be able to get a longer axle and use spacers with 130mm hugs but I don't know what kind of dish you'd have on your rear wheel to support that and what that would mean for wheel strength. How many grams are you going to save by using 130mm hubs?
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Old 08-18-11, 07:51 PM   #3
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You can't change the dropout spacing of an aluminum frame but you can easily adapt some single-bike wheels to fit in the 145mm spacing by installing a longer axle and appropriate spacers. Shimano cup-and-cone hubs work very well for this because they use plain threaded axles that can be easily removed and replaced. If you're me, you'll want a traditional spoked rim with 32-36 wire spokes because that's the only type of wheel I know how to mess with. Loose Screws has the axles -- you need a axle that's at least 150 mm long so that you have a couple of millimetres protruding beyond the faces of two locknuts to engage the dropouts. (A stock axle will have about 5 mm protruding but you don't need this much.) Be sure to get Shimano threading which is 10 mm x 1 mm pitch, not Campagnolo's 10 mm x 26 tpi.

Install the axle so that all the additional "width" is on the left, non-drive side and re-centre the rim. The wheel will now have much less asymmetry ("dish") in spoke tension and will probably last longer in your tandem than it would in a single bike. If you are meticulous about the exact arrangement of spacers on the right, cassette side to match the wheel that's in your tandem now, you should be able to switch wheels without having to make any adjustments in the cage stops of the rear derailleur or in the indexing.

I doubt that doing this will make you any faster but it is fun to have a set of lighter wheels that you can swap in or out as the mood dictates.
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Old 08-18-11, 08:03 PM   #4
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Heat treated alu frames are near impossible to cold set.
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Old 08-18-11, 08:12 PM   #5
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You could narrow a Cannondale without too much effort. Find some 7.5 mm aluminum plate, or have some machined to thickness. Use something fairly strong, at a minimum 6061 t651. 2024 t351 or 7075 series would be stronger. Using the oem dropout as a pattern, replicate that on your new plates. Using existing frame holes, you can secure these new plates to the oem dropouts. I will recommend some quality fasteners, not an inferior product but a true American made allen head bolt. You may need to use flush screws and a step for the der hanger, possibly it could sandwich between the dropouts , should not be a big deal to machine.

Obviously running a 145 axle is optimum, however the 130 should be fine using a 145 quick release.

This is not a simple bike shop project or for someone with lacking fabrication skills. A decent machinist or tinkerer with a Bridgeport could get this done pretty quick.

PK
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Old 08-18-11, 08:31 PM   #6
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Thank you, its more on the type of modification that I would like to do.
I just need to figure out how would I secure the plates to the dropout, will go see on the bike, maybe I will undertand.

No drilling involved in the frame to fasten the plate? just trying tu understand exactly how would I fix the plates.

Thanks




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Originally Posted by PMK View Post
You could narrow a Cannondale without too much effort. Find some 7.5 mm aluminum plate, or have some machined to thickness. Use something fairly strong, at a minimum 6061 t651. 2024 t351 or 7075 series would be stronger. Using the oem dropout as a pattern, replicate that on your new plates. Using existing frame holes, you can secure these new plates to the oem dropouts. I will recommend some quality fasteners, not an inferior product but a true American made allen head bolt. You may need to use flush screws and a step for the der hanger, possibly it could sandwich between the dropouts , should not be a big deal to machine.

Obviously running a 145 axle is optimum, however the 130 should be fine using a 145 quick release.

This is not a simple bike shop project or for someone with lacking fabrication skills. A decent machinist or tinkerer with a Bridgeport could get this done pretty quick.

PK
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Old 08-19-11, 03:08 AM   #7
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Just like this.
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Old 08-19-11, 08:03 AM   #8
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Just like this.
Exactly, he may need to do something similar for both sides wanting to get to 130mm (7 1/2 mm per side).

I would also consider adding a fastener with the rack hole on each side. The left side will need it anyway so the plate does not fall off when the wheel is removed.

PK
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Old 08-19-11, 09:02 AM   #9
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ok, thank you all, I understand what I will need to do.
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