Stronglight 49d query

Hi all,

I lost two bolts today (the ones next to the bb, or centre of the chainring that connects to the driveside crank arm). Heard them go, not good. I won't be riding this bike tomorrow!

so the questions are, why would they break, where can I get new ones, and any tips for removing ones that have rounded off and can't be unscrewed?

thanks

They break because they are old corroded steel with a high shear load applied by your awesome legs*.

TA Cyclotourist bolts should fit as a replacement
http://www.spacycles.co.uk/products.php?plid=m2b34s173p222

*awesomeness of legs not required when the bolts have such a small pcd

cheers...

mdcc got the bolts, already on bike again. cheers for tip

Am also looking for some help with a 49D issue:

Any rough idea what size BB i'd need for fixed on 49D single chainring cranks?
I'm guessing around 110mm ISO BB

Rear chainline is 42mm (Rear dropouts 120 spacing, campag pista hub and I've measured it 3 times) with a standard british threaded bb 68mm

I have a Shimano UN54 115mm that i've been trying to use as a guide.
But as it's JIS i'm wondering how much use it is to get an accurate measurement.

Any help much appreciated, i've searched the interwebz but with no success.

This diagram suggests that 111.5mm would be the OE fitment for Cyclotourist Piste (if you'll forgive the oxymoron)

Which may or may not be useful.

I'd suggest assembling it onto the 115mm UN54 and measuring the resulting chainline, then get whatever size of UN54 (or the *NEW IMPROVED*™ BB-UN55) looks like the most likely candidate to bring everything into line, probably the 110mm

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Thanks mdcc_tester
will do

(the UN55 would be an improvement if they stopped using those rubbish plastic cups)

(the UN55 would be an improvement if they stopped using those rubbish plastic cups)

The UN55 is an improvement because they stopped using those rubbish plastic cups.

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I have 111mm on my bike with a 49D set on :) You could probably get away with 110mm and shim that side out if need be.

Hardly needs shimming for the sake of 0.5mm of chainline, and standard BB shims are 1mm so you'd only be going from +0.5 to -0.5 anyway :-)

Thanks for the help.
I'm going to have to replace the current BB - but should I get an ISO or JIS one?
Velobase says 49d is ISO...

I use a stronglight one ISO I believe http://sheldonbrown.com/bbtaper.html

And Sheldon Brown's erroneous article claims another victim...

The squares on the ends of JIS and ISO axles are the same size, ½" or 12.7mm, and the taper angle is the same 2°. Some ISO axles have a 45° x 1mm chamfer beyond that, making them effectively 2mm longer overall than the JIS BB giving the same chainline. This extra length should be irrelevant, unless you crank tapers are so worn that the crank bolt bottoms out on the axle extension, in which case it may be impossible to correctly tighten a JIS crank onto an ISO axle, but there should be more clearance than that on components made to correct tolerance and in good condition.

The BB-UN5x is such good value for money that there would need to be exceptional circumstances to use anything else, and the mere (nominal) difference between JIS and ISO isn't such a circumstance.

And Sheldon Brown's erroneous article claims another victim...

.

:D

I tend to use the Stronglight ones now since I ruined a chainset on the wrong BB, the angle was slightly different and it worked loose wearing out the drive in the crank.
I think it's a bit like 1/8th chain/sprockets mix & match with 3/32 they can swap one way but not the other.
I could be wrong though :)

which stronglight bb do you find works? for single 49d

which stronglight bb do you find works? for single 49d

http://www.spacycles.co.uk/products.php?plid=m2b2s110p140

You can always drop Spa Cycles a line and ask, they are very helpful

thanks i'll check it out

http://www.spacycles.co.uk/products.php?plid=m2b2s110p140

I think you'll find all current (and recent) JP400s are JIS, not that it matters. Although the discontinued Stronglight SBB was so lovely that it was worth paying a premium, and it was made in ISO form, the JP400 isn't really any better than a Shimano BB-UN-5x

MDCC looks like you are right a quick double check on Google shows some people use a UN52 BB

I also found these could be helpful;
http://www.lfgss.com/thread47888.html

http://www.classiclightweights.co.uk/components/ta-cranks-comp.html

anyone had problems with the driveside crank getting too close to frame so when you tighten the bolt it hardly turns? I assume I need a longer bb?

I assume I need a longer bb?

Correct. I don't think there was a lot of clearance to start with, as the crank/ring is flat all the way out from the axle unlike modern cranks, so a bit of wear on the tapers will close the gap to nothing.

Correct. I don't think there was a lot of clearance to start with, as the crank/ring is flat all the way out from the axle unlike modern cranks, so a bit of wear on the tapers will close the gap to nothing.

would a 115 solve this do you think?

What have you got at the moment? If the crank is properly tight and barely grazing the BB cup flange, you only need about 1mm extra, so +2mm assuming a symmetrical axle.

111?

Yes, that's a 111mm. The UN55 comes in 113mm and 115mm flavours, so take you pick based on how much extra you think you need based on the current degree of interference
http://www.chainreactioncycles.com/Models.aspx?ModelID=71369