Another short answer :- go to www.reliablespring.co.uk and use the calculator, that way you can work out the effect of removing coils on spring rate. No need to reinvent the wheel.
Mac
FF: Forks Modified Steering Stem
- Thread starter greg brillus
- Start date
Mac
Chris, the bikes I have ridden have had either, Koni's, Thornton's, and original Vincent type shock's (although the Vincent one is one of the newly made ones not an original) The differences are a bit subtle and I am only test riding them for a distance of about 10 km's (6 miles or so) I guess you know the Koni's are adjustable. I don't think the change in shocks has as big an affect as the springs themselves, but I have several bikes and multiple springs of many different rates to try which is a big help. It is hard for me to predict how a bike will behave with a heavy rider, but I have tried a pair of David's red (75) lb springs which works well and I feel would suit a heavy rider, with a small amount of packing (less than half an inch in each spring box) and easy to install at probably about 20 mm of pre-load, this feels a bit too much for a light rider but not unacceptable, so probably ideal for a heavy person. Cheers..........Greg.
Greg, I've been out this week with AVO, Armstrong, Koni and standard dampers, I think there may be a problem with my AVO as there is NO compression damping even by hand, it's gone back for them to have a look at, the standard and Armstrong dampers are nice and much the same as each other giving a lovely ride but the Koni is much rougher over the smaller stuff even though it has much the same performance on hard impacts such as potholes and speed humps.
I'm concerned much stronger springs would compromise the ride I have as it's just the really hard braking that's the problem, but I may have to start in that direction but I'll try the inners first.
The Koni was on the softest setting but adjustment only effects rebound as far as I can tell, a Thornton would be nice to try but I don't know anyone with one.
I'm concerned much stronger springs would compromise the ride I have as it's just the really hard braking that's the problem, but I may have to start in that direction but I'll try the inners first.
The Koni was on the softest setting but adjustment only effects rebound as far as I can tell, a Thornton would be nice to try but I don't know anyone with one.
Well, Rob's answer is excellent, much better than my memory, but it was more the process and some of the terminology that sticks in my memory.
At one point I thought about doing a rear spring that was more like a stock Vincent. I wondered if the ends of the Vincent rear spring brasses captured more of the spring to make the last coil fully inactive. Like Chris, I wanted rough calculations unless I was dragged into more detailed ones. If I were testing a rear spring on a press with a scale, I would leave the brass ends on to get the best spring rate readings.
David
Right back when I first started with AVO they tested some standard springs complete with brass claws for me. I was curious if the conical ends made the spring progressive. The answer was no, they were linear right up to the point they went solid. The spring rate for the both the original and Spares Co springs were nearly bang on the spec. 195 lb/in from memory.
Chris I would say you probably only need a change to the springs by a relatively small amount. For example going from 45 to 50 lb springs, so installing the inner springs may give you the result you need. I don't feel that no matter how soft the springs are, the bikes still feel quite heavy in the front end, unlike the Comet's which the change using the new stem and softer springs makes a huge difference. Cheers...........Greg.
Rob,
That is good information. I always thought the spring would be linear rather than progressive, but I was not certain. It was claimed to be progressive, but it seemed like a subtle difference in coil diameter that might be averaged. I have some Brampton front springs sitting here that I have meant to try on the press to see if they are linear also.
David
I found this in my stored favorites and had not seen it in a while. It was originally linked here by hadronuk in 2013. I thought I would post the link again for those who might not have seen it. It puts things in perspective, and is a good visual aid. The standard fork motion is really obvious, and the front mudguard even touches the magneto cowl. Nice to see the seat motion too. I wonder if this apparatus still exists? Thornton Suspension Institute? I would love to see the new suspension mods discussed here run on it and compare. Best to watch full screen. Nice musical editing too.
Hi Greg, installed a second C outer spring and went for a run round my test circuit getting a total of 2-1/2" of travel under hard braking, this still leaves me a bit of travel for hitting bumps while hard on the brakes so that's about right I think.