Delinquent
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| posted on 4/11/07 at 12:36 PM |
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Scrub Radius V's KPI
If you had to increase scrub radius or KPI to achieve a workable solution... which would you go for, and why?
I'm unfortunately lacking a few mm clearance (unless I want to skim about 40mm off the diameter of the brake discs  ) so have to do one or the
other. At present I have 30mm scrub, 4 deg inclination - I'd have to increase scrub to roughly 50mm to get the clearance I need, or increase the
inclination to around 9 deg.
Either that or bin the hub / disc / calliper / wheel choice and start it all again from scratch. Which I really don't want to do.
ETA - one other thing I could do would be to increase the overall height of the upright, to put the lower ball joint below the brake disc, and
combine with a moderate increase in both KPI and scrub to 6 deg, 35mm...
EATA - or I could make the upright really really short and have even less of an increase in both....
[Edited on 4/11/07 by Delinquent]
[Edited on 4/11/07 by Delinquent]
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Cousin Cleotis
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| posted on 4/11/07 at 04:27 PM |
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How would each effect the roll centre? This may make the decision easier.
What uprights are you using to be able to alter the KPI?
Post some pictures of your suspension, threads like this can be a little boring......
Paul
[Edited on 4/11/07 by Cousin Cleotis]
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gttman
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| posted on 4/11/07 at 04:41 PM |
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Del
I made my own disc bells but I'm actually sure the std discs would fit though so I actually question if you are going OTT with the scrub
radius.
I know that the books tell you that zero scrub is optimum, but you also have to bear in mind the steering 'feel'.
Andygtt
Please redefine your limits
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Delinquent
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| posted on 4/11/07 at 07:14 PM |
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I did wonder if I was overly concerned about that Andy - just concious of going too far the other way in adding the feel. In my research going on an
average of what each person reckons is a best trade of feel for performance, 30mm came out quite popular. If I go to 40mm I can get all the clearance
I need with just an increase in KPI to 5 deg so I'll give that a try - if it turns out to be cack I can always have new uprights made later!
Cleotis, sorry for it being boring, don't have photo's at the moment as it's all in CAD at the moment. Here's a little screen
grab for you of the test-bed though. (note, this isn't the finished structure, it's just what allows me to work everything out.)
 
Rescued attachment frontsusp.jpg
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andygtt
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| posted on 4/11/07 at 08:10 PM |
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Looks similar to mine in angle and possition...
What offset do you intend to run?
Andy
please redefine your limits.
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Delinquent
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| posted on 4/11/07 at 09:06 PM |
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going for the turbo wheels so 45 - could go to the standard wheel but it only gains me another couple of mm once it's all panned out.
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andygtt
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| posted on 4/11/07 at 10:44 PM |
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sounds good, not far different from my setup in the end then.
Andy
please redefine your limits.
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Delinquent
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| posted on 4/11/07 at 10:52 PM |
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no indeed, I just went a very long route to get to the same end instead 
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