Vintage Dirt Bike Q & A

Hi guys, can anyone tell me a good setting for the rear suspension sag on a 79 red rocket fitted with ohlins and set up for a rider of approx 70kg who would be considered of medium / fast race pace.

Since nobody is offering any specific cr250 info, I'll chime in with generic guidelines.

1/3 of travel is pretty normal. If your bike runs 12" of travel, start the sag at 4".

If you dial in that amount of loaded sag and the unladen bike has about 1" of sag - without you on it, you have a good starting point.

If your 4" of sag leaves the bike with no unladen sag, then your spring is too soft and you had to overpreload it to get your proper race sag.

If you end up with much more than 1" of unladen sag, then your spring is probably too stiff.

Hope that helps! And is that how you spell unladen?

Low pressure (upper valve) - 75-85 lbs
High pressure (lower valve) - 125 - 140 lbs

I am 185 lbs + gear and run 80 lbs + 140 lbs. You are 154 lbs (70 kg) so I would start with the lower numbers and work upwards. Get yourself a MTB shock pump and check that it is the kind that does not lose any air pressure from the shock as you disconnect the pump.

You will find plenty of procedures on the Internet that will take you how to set race and static sag, but these are all oriented towards bikes with coil + air shocks. I think you may find that if you go with that standard 4" (100-110mm) approach you may find you are way off on the pressure settings above. If so go with above and if the bike sags too much at the rear, move the forks up in the triple clamps to compensate.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF