1990 SM400

[FPrue1304]

So I started some research about what to do with my old SM400 from 1990.

I posted before here: http://community.vintagecannondale.com/threads/hi-from-europe.664/

I am considering to turn this into a "Gravel Bastard", see this picture. What do you think how this set up would ride?



It fits me pretty well, but would need to replace with a shorter stem (approximately 70 mm).

 

[FPrue1304]

I would definitely convert to a 1x system. I noted that the frame has a 130 mm rear dropout, a 68 mm BSA and a stack value very similar to my road bike. Only the frame has a vastly larger reach which however can be aligned with a proper stem. So, essentially, this frame has a lot common with a road frame what made me wonder whether I would be able to fit a road 1x crank to it - and it works!

This is a SRAM Red AXS crank with 170 mm. I would go for a 165 mm crank on this frame, for some more clearance.



Anyways, the crank works and there is about 90 mm space for a single chainring, what translates to roughly a 42t size - just perfect for my purposes!





Next steps would be to strip down the frame, repaint and then look for some proper parts and a wheelsset. I am not in a hurry...

 

[black lightning 1987]

Should make a nice gravel bike. Be sure to smooth out all the gouges on the drive side chain stay to reduce the chance of cracking.

 

[FPrue1304]

Hmm what involves in your view smoothing them out?

 

[black lightning 1987]

I would start with files to get the rough edges smoothed down. From there I might use sanding discs or perhaps hand sand.

 

[FPrue1304]

Makes sense. I was only going to smooth the roughest and generously use filler because I did not want to take off too much material. But is there a concern re structural stability?

 

[black lightning 1987]

Any surface scratches can lead to stress being concentrated and ultimately cracking.

https://en.wikipedia.org/wiki/Stress_concentration

 

[FPrue1304]

Yes. Makes me a bit concerned whether it is worthwhile to put energy into this.

two questions

opposite of the cable stop on the right rear chain stay is a small screw. What is the function of this screw?

How do you non-destructively remove the black cable guides on the top tube. There are two intact ones left.

 

[black lightning 1987]

Is it a screw or a rivet on the chain stay? Either way I think its function was to plug a vent hole during the welding of the frame.

I think you need to push the plastic pins through the cable guides with a small punch. It's not something I have done but you can probably rattle the pins out of the frame and use them again.

 

[FPrue1304]

It is definitely a screw. I took it off but nothing happened. I thought it might hold the cable stop in place.

Re guides: OK might be difficult to get them out of the frame, need to check if there are holes in the head or seat tube. I already bought a set of new ones from this website.

 

[MEENI]

Tip: just push them in the frame and flush them out with water, works great
Migt be thet jou can not use them annymore but the cam be replaced with somethong els
I used verry small nails once and just gulued them on the frame with superglue

 

[FPrue1304]

I have made progress, we sanded down the frame and it is ready for paint. We filled up the scratches with epoxy to avoid taking off any aluminum.

Seems like I sadly lost the screw-on cableguide underneath the bottom bracket. On the web I find a part with the number KF002 from numerous sources, readily available. It seems to be a clip on version. Would that fit? I might only need the guide for the rear cable as I am looking at a 1x set up.

Thanks!

 

[black lightning 1987]

Pretty sure a standard Shimano or Campagnolo guide would work.

 

[FPrue1304]

I never got around to finishing this project through last year. Too much ccycling.

Getting now back to it. Next step is to paint the frame.

Meanwhile the headset:

I measured the inner diameter of the headstone 30mm plus a tiny fraction that I cannot really read on my gauge. The inserts of the old headset clearly have a diameter of 30.2 mm. So I go with a 30.2 mm headset again, I guess? (And this is the common size, it is hard to find a 30 mm headset, I think only Aliexpress has some, but wouldn‘t this apply to some Asian frames?).

Best, Felix

 

[black lightning 1987]

30.2 is what you want. Headset cups are designed to be slightly oversize so they don't wear and begin to rattle around. The acceptable range for the inside diameter of the head tube is 30.05 to 30.1 mm.

 

[FPrue1304]

Thanks!

 

[FPrue1304]

So my project has taken an unexpected turn. Found this frame, essentialily the same 3.0 version, built 6 months earlier, also 130mm dropouts, BUT: 18 inch. My current one, 20 inch, was on the bigger side for me.

One goodie I hope for: the head tube is much shorter, so my existing Pepperoni fork shaft will be too long. I hope long enough for clamping on an ahead set stem. With 2 inches less ground to top tube height, I am hopeful.

Very excited, I must say, how this will turn out.

 

[black lightning 1987]

It's a shame to cut a fork down if you can avoid it. I generally just add spacers even if some end up on top of the stem. See if Brian has any forks left that are long enough for your frame. That green looks nice. Are you going to stay with it?

 

[FPrue1304]

I am not planning to cut the fork. I plan to use the excess part of the fork shaft for clamping on an aheadset stem (probably with a 1 in to 1 1/8 in shim). The height of a stem is typically 4 cm, if there is excess length I will add a spacer under the stem. But let’s see. I heave not found any documentation about the lengths of the head tube.

I plan to go with viper red.

 

[black lightning 1987]

Viper red always looks good. I have a 1993 M800. I can't think of another Viper red bike in the collection despite it likely being the only color that was used for as many model years.