I'm planning on putting stiffer springs in the forks - stock springs are 30mm outside diameter, replacement ones are 29mm diameter. The tube inner diameter is about 31mm. Does the decrease in spring diameter matter? Seems to me if you take a long spring, compress it, it tries to buckle, which then puts more pressure and more friction on the tube, so I'd rather get springs the right diameter. Does anyone have any ideas on this?


Thanks!

 

spring diameter does not matter, only the spring value=k matters. springs can be made in various shapes and forms, flat springs, behive, round, tapered, etc. so long as the k value is correct, wire dia does not matter. over the length of the spring will it buckle or waver. but when the spring is compressed into a finite space, it won't matter. it's not like the spring is going to go anywherebut along its vertical axis. some springs, depending on make, the spring coil (not spring wire) will increase in diameter slightly.

what replacements were you looking at? are you racing or just need to replace old set. i was using racetech but i do not know measurements off hand.

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i don't know if you have taken a look at a fork diagram. but in the assembly you will see a longish tube atop thespring. that is the spring collar. now, racetech springs are 375-380 mm, free length. the actual set compressed length of my springs are shorter because in order to preload the springs to my weight, i had to replace the spring collar with a longer one in addition to compensate for the addition of valve emulators.

this is a link to fork assembly diagram. http://fiche.ronayers.com/Index.cfm/...ycle/MakeID/1/
Make/Honda/YearID/30/Year/1989/ModelID/6530/Model/CBR600F/GroupID/274041/Group/FRONT_FORK

i understand your question of getting something that is close to max inner dia. but that isn't necessary. there is no downside to a smaller dia coil spring, especially if less than a 1mm. and with it all being submerged in oil, not a lot of friction between spring coil and fork tube.

 

Yeah, OK I was probably seeing a problem with the diameter where there really isn't one. My existing (stock) springs are OK but just too soft. I was looking at chucking some stiffer (Racetech or similar) ones in and when researching it found they were smaller diameter so thought I'd ask the question.

I occasionally use the bike for track days... not often enough, but also ride it as quick as I can (safely...) a fair bit on twisty roads.

Thanks for the info!

G

 

you may want to take a look at Progressive springs. unlike racetech that uses a linear spring, progressive uses progressive springs or a tighter winding and spacing as it nears the ends of the springs. i believe they cost less as well. right now, i have a set of progressive springs in my current setup. they seem to work pretty well. the more compression, the firmer the feeling. i think this is the better way to go if you are looking for something stiffer especially the more the front end compresses.