captain chaos Posted November 11, 2008 Share Posted November 11, 2008 Following my re-build I had my first outing to the Ring a few weeks ago and I'm now just giving the car a check over... i've taken the rear wheels off and noticed that the tyre (ACB10) has taken the powdercoating off the radius arms in one spot and left a thin heat line on the inside tyre wall. There was no sensation or noise whilst driving and and it can only be fractional because the trye size info which is on the same radius as the heat line is only slightly worn... In a static position there is 13mm of clearance, which at first glance you might have thought would be enough...I made myself a pair of 2mm spacers over the weekend to provide a bit more offset.. Has anyone else had any tyre rubbing issues with the CXR's purchased via Blatchat? and if so, what level of clearance did you eventually require? Link to comment Share on other sites More sharing options...
Rob Walker Posted November 11, 2008 Share Posted November 11, 2008 TADTS you need 30mm+ to avoid any contact. Rob Edited by - Rob Walker on 11 Nov 2008 20:09:09 Link to comment Share on other sites More sharing options...
A10ROX Posted November 11, 2008 Share Posted November 11, 2008 agreed TADTS R400 with Barnby & Avon slicks A10ROX now garaged with D10ROX (Red GT3)! Link to comment Share on other sites More sharing options...
martinwhitcher Posted November 12, 2008 Share Posted November 12, 2008 what year is your car? the dedion tube widened by 10mm in 2002 i believe... how do i know..... just had the same on my car running mb wheels and avon slicks. have new tube waiting to go on. Martin MW 51 CAT Superlight No.171 now known as:Superlight DVA 250 Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 I've just fitted a brand new DD tube... These wheel were to suit a superlight so If I need 30mm min clearance( as mentioned above) the offset must be way out...I'll check my other wheels. In the meantime it looks like i might need some bigger spacers, and some longer wheel studs! Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 My CXR rears are 8.5 x 13 with ET24 stamped on the inside. I'm getting radius arm rub worth about 1mm. (it is just marking the tyre...but that was from a damp lap of the ring and not a hot lap at spa where i would expect more tyre deflection) With the ACB10 on the wheel, it is leaving me with a radius arm clearance of about 12/13mm. To achieve a clearance of 30mm (as recommended above) I need to take the ET down to ET7 which I can't see anywhere in the archive as required. I can see ET12 being spoken about, but not 7.... I've ordered some 15mm spacers which will get me to ET9 and from my mock up's they seem to fit Ok... I take it i've looked at the ET issue correctly? and are you sure I need 30mm+ radius arm clearance? Cheers Gary Link to comment Share on other sites More sharing options...
DaveK Posted November 13, 2008 Share Posted November 13, 2008 Gaz The spec i have listed for the MB split rims is as follows 6.5x13 - 110mm backspace 8.5x13 - 140mm backspace The caterham 8 spoke are as follows 6x13 - 113mm 8x13 - 140mm Dave Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 Thinking about it again...the ET is relative to overall wheel width so my ET calcs are not right... Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 cheers Dave Link to comment Share on other sites More sharing options...
Rob Walker Posted November 13, 2008 Share Posted November 13, 2008 The offset that you have is correct and the standard Caterham ET24. Do you have the radius arms with the swaged area to give extra clearance for the tyre? Also BIM that reducing the -ve offset will put higher loadings on your wheel bearings and its likely that your tyre will contact the outside lip of the wheel arches when the suspension is in compression. I run with the CXR`s -ET24 8.5" and have only had a problem when running massive Yoko slicks 200 515 /13. Also note that Caterham now use 8" rear wheels with ET24 offset. Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted November 13, 2008 Support Team Share Posted November 13, 2008 Measure the backdepth (distance from hub face to edge of inner rim) - that is the critical measurement. DaveK's values above square with what I measured my Caterham 8 spokes to be (111mm and 139mm respectively). At those you shouldn't be getting any rubbing on the radius arm especially with the new de-dion tube. The radius arms have a hollow on them - is that facing outwards? Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 Hi Shaun, I spoke with Compomotive and I'm a bit clearer on where I am now....it seems I bought these wheels in good faith from the 'for sale' section...."to suit a superlight"...I should have looked harder at the ET's which I failed to do...it's my fault...the wheels are fine for road use but not for track work. Spacers will sort...it's just yet another mod, albeit a small one. Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 Sorry Rob, I replied to Shaun before reading your post! Rob, All I can say is that I have 8.5 rears with ET24. My radius arms are not swaged ....so I went to the CC site and ordered a pair these should help....Thanks My Image wheels, which i have 2 sets of, have a backspace of 140mm instead of the 120 on the CXR's which I why I've not had the problem before... Gary Link to comment Share on other sites More sharing options...
captain chaos Posted November 13, 2008 Author Share Posted November 13, 2008 I've looked in the archive trying to find a confirmation of how much longer the new DD tubes are.. Ian's exhaustive work on failures (thread in archive) adds that the lastest version had it's length increased by 8mm to harmonise with the SV's...yet on another thread someone measured one and it had increased by 20mm Does anyone know for definate what the increase was...8mm overall or 10mm either side (20mm overall)? Cheers Gary Link to comment Share on other sites More sharing options...
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