precad

Dear readers,

Disclaimer: I've owned two 1984/85 cannondales, one 1987 criterium series cannondale, as well as one CAAD4, one CAAD5 and two CAAD9s. That is a lot of different frames with the same observation - maybe you can help me out (read below)

What I noticed is that the rivnuts for water bottle cages on vintage cannondales (ALL OF THEM) seem to take what appears to be some sort of thinner version of M5 bolt. All the M5 bolts that came on vintage frames I've purchased in 2000's appear to be specific to that era, as the regular water bottle allenhead bolts that all the CAADs use do not go in as well. Pitch and the allenhead tops appear to be identical between new and old bolts.

I've observed this seemingly on every frame of the two groups (the vintage and the CAAD). Recently I even purchased some lightweight aluminum M5 0.8pitch bolts from an online bicycle supplier. As I predicted, these went just fine into new frames, all the way to the bottom, but they had trouble going into the vintage cannondale (n=1 for this test). Upon observing the aluminum threads, after going in about 6mm, the threads further up appear rounded. Furthermore, I've pulled out my bolt collection for water bottle bolts that are recent and have been used on new-era frames, and none of them would have an easy time to go in the vintage frames. I am afraid to force them deeper and it takes just about two turns for the bolts to start being really tough to push in further.

Taking the rivnut bolts from vintage frames - they are noticeably (though not hugely) looser in the new frame (CAAD9).

IS THERE AN EXPLANATION FOR THIS? This is extremely frustrating.

many thanks,

precad

rccardr 

Have had the same experience, you are not crazy. You'll have the same experience with rack and fender bolts, BTW.

I believe that at least some of the bolts (and threading) they used were SAE and not metric.

Glennfordx4

At a thrift store a few months ago I picked up a big NOS Rivnut kit for $15 & was excited, until I got home and realized they were all standard thread rivnuts.

Glenn

rando_couche

Yep. BITD, Blackburn sold stainless button-head screws for use with fender eyelets and bottle bosses. They fit just fine, but took 1/8" allen wrenches, not metric. Come to find out they were SAE 10-32, not m5x0.8. 10-32 screws work fine in m5x0.8 threaded fittings/nuts, but not the other way around - 10-32 is just "that much" smaller than m5, what Sutherland's calls a "class B" fit. I'd be willing to bet the rivnuts in your C'dale are 10-32. (Metric was still not all that available on this side of the pond 25-30 years ago.)

SP
OC, OR

DMNHCAGrandPrix

Try some 10/32 bolts. These "inch-based", size 10 bolts measure 3/16 inch by 32 threads per inch, which would be M4.83 x 0.794 in the metric system. For comparison, an actual M5 bolt is 5.00 x 0.8 mm (slightly bigger in both diameter and pitch, so will be over-tight when screwing into a non-metric version).

precad

thank you very very much folks, this is very helpful. I had an inkling of an idea that the bolts were not metric, but didn't want to believe it.

regarding the whole 25-30 years ago thing - it hurts to hear that. Time is moving too fast, and I don't know where all of this is going.

dddd

I've actually tapped out the 10-32 fittings on Vintage Cannondales (and on certain Raleigh Techniums iir) using an M5x.8mm tap.

The one on the Raleigh Team 753 Technium was for the seatpost collar clamp iir.

Some of these nuts are hard to tap because of very hard material, so be cautious not to spin the rivnut or break the tap, using oil of course.

Even back in the mid-1980's, I thought that Cannondale was silly for still using SAE fittings on a road bike, and I especially disliked the need for an SEA hex wrench.

pastorbobnlnh 

I ended up doing the same, re-tapping to metric. IIRC, I had to because I had botched up the threads using metric screws in the first place.

auchencrow

I would be very circumspect about tapping out a rivnut in an aluminum frame.
Why not just use proper SAE 10-32 screws?

repechage

My guess why they used 10-32 instead of M5 was cost, in the USA, SAE fasteners are cheaper and easier to source. For the functions required, not a problem mixing the standards on the bike.

I have run into this before with larger fastening bolts and nuts, and there the cost difference can be quite noticeable to a products cost.