georigg Posted July 23, 2008 Share Posted July 23, 2008 As everyone knows, Aerotops suffer to some extent with skuttle-shake......take the roof off and you lose body stiffness. When I bought my Aero last year it came with new tyres already fitted, Bridgestone 225/50-16 all round, but even after fitting a Carbing front strut, it still "shaked", feeling like it was hinged in the middle at times, but only when the roof was "off". However, Ive just fitted a set of 18" x 8.5 rims and new tyres and the car really feels like new, its like driving on silk! Even with the roof off, its just as smooth. So if any of the Aero owners on-site have this problem, its worth while having a look at your tyres as a possible source of the dreaded shake with the roof off. It certainly has worked for me! Rgds Georigg Quote Link to comment Share on other sites More sharing options...
michael Posted July 23, 2008 Share Posted July 23, 2008 I don't see how new wheels and tyres can solve the problem of the car having a big hole where a structural panel should be *shrug* Sounds like they are masking the issue rather than fixing it. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted July 23, 2008 Share Posted July 23, 2008 Do you still have the same sized tyres on all 4 wheels? Quote Link to comment Share on other sites More sharing options...
Gruggs Posted July 23, 2008 Share Posted July 23, 2008 I don't see how new wheels and tyres can solve the problem of the car having a big hole where a structural panel should be *shrug* Sounds like they are masking the issue rather than fixing it. I'm with you on this one. My aerotop "skuttles" as well. I would have thought the only way to sort that is to ensure that the front and rear of the chassis are connected to reduce the flexibility, namely through a cage? G Quote Link to comment Share on other sites More sharing options...
JustGav Posted July 23, 2008 Share Posted July 23, 2008 I don't see how new wheels and tyres can solve the problem of the car having a big hole where a structural panel should be *shrug* Sounds like they are masking the issue rather than fixing it. I don't fully understand what he said either if I'm honest... The issue would just be masked by the lack of side wall... As you have said, taking out the roof does mean all chassis strength is in the lower half of the body which will not stop twisting forces regardless of tyre size. Quote Link to comment Share on other sites More sharing options...
Ewen Posted July 23, 2008 Share Posted July 23, 2008 Er....no. Quote Link to comment Share on other sites More sharing options...
AndyT Posted July 23, 2008 Share Posted July 23, 2008 Do you still have the same sized tyres on all 4 wheels? Bit of a no no bud. Quote Link to comment Share on other sites More sharing options...
dangerous brain Posted July 23, 2008 Share Posted July 23, 2008 Mine was reduced considerably by fitting a front strut brace. I imagine that there would also be benefits to fitting a do-luck centre brace and a rear brace. Quote Link to comment Share on other sites More sharing options...
Branners Posted July 23, 2008 Share Posted July 23, 2008 out foul spot... moved out of technical as its not really technical. Quote Link to comment Share on other sites More sharing options...
TRACIE_LOU Posted July 23, 2008 Share Posted July 23, 2008 we have new wheels and tyres plus front and rear strut braces and still get shake be it slightly reduced Quote Link to comment Share on other sites More sharing options...
dangerous brain Posted July 23, 2008 Share Posted July 23, 2008 I'd suspect that if new wheels and tyres made it better then the old ones had some serious balancing issues. Quote Link to comment Share on other sites More sharing options...
jevansio Posted July 23, 2008 Share Posted July 23, 2008 I'd suspect that if new wheels and tyres made it better then the old ones had some serious balancing issues. Quote Link to comment Share on other sites More sharing options...
TRACIE_LOU Posted July 23, 2008 Share Posted July 23, 2008 im sure the wheels do little to reduce the shake but we have noticed a slight improvement Quote Link to comment Share on other sites More sharing options...
gordy07 Posted July 23, 2008 Share Posted July 23, 2008 mine shakes too with brand new tyres and balanced wheels,ive just learned to live with it. I stay in scotland so its not as if the roof is off that often! Quote Link to comment Share on other sites More sharing options...
georigg Posted July 25, 2008 Author Share Posted July 25, 2008 Didnt realise this post had been moved, so not able to comment further until I did a search today. The "old" wheels were standard "16" but when I bought the car last year it had been fitted with a new set of Bridgestone Mud and Snow tyres.....standard size 225/50-16. The M&S tyres were block tread, & capable of being studded, so they were "noisy";the block tread design resulting in insipient vibration, due to their design(dont ask me why they had been fitted by the seller!). I had already fitted a Carbing front strut and although there was an improvement after fitting, there still was a problem with the roof off. The new tyres are pure road tyres & changing the wheels and tyres has much reduced shake(tyres are 225/35-18 front & 235/40-18 Rear on Team Dynamics 18" x 8.5JJ Rims). Going back to tyre in general, on a previous Supra I had fitted Goodyear Eagles and one front tyre developed a quite dangerous shimmy above about 70MPH which could not be balanced out. Further investigation through a good friend who still worked in the industry showed that the tread join on the uncured tyre carcass had been joined "un-evenly" with a thick part at one side, thinning across the tread to the other side of the tyre. When cured, the tyre looked OK and was sold as first quality but investigation showed that one sidewall was "thick/heavy over about 100mm, thinning across the tyre to the other sidewall which was thinner than standard, & causing a harmonic to be set up, both rotationally and dynamically which at 70MPH matched a critical frequency for the suspension set-up. This brings me back to the original point of the post; do not discount tyre induced vibration when looking at ways to reduce skuttle shake...............skuttle shake is after all caused by vibration frequencies approaching the natural frequency of the(less stiff) car body and becoming amplified under certain conditions. Removing or changing the frequency of vibration will result in the "shake" occurring at a different set of conditions and lead to a smoother ride at normal motoring speeds. Fitting pure road tyres in place of the M&S tyres fulfilled this requirement, with the stiffer sidewall of the lower profile tyres and smoother tread working together to remove the previously induced vibrations coming off the M&S tyres. Sorry its a bit techy an answer, but it does work ! Quote Link to comment Share on other sites More sharing options...
supra_aero Posted July 25, 2008 Share Posted July 25, 2008 wierd, my roof never shakes. and certainly not with roof off. You sure you are tightening it up properly with a proper hex key spanner thingy? Quote Link to comment Share on other sites More sharing options...
supraGZaerotop Posted July 25, 2008 Share Posted July 25, 2008 (edited) As everyone knows, Aerotops suffer to some extent with skuttle-shake......take the roof off and you lose body stiffness. When I bought my Aero last year it came with new tyres already fitted, Bridgestone 225/50-16 all round, but even after fitting a Carbing front strut, it still "shaked", feeling like it was hinged in the middle at times, but only when the roof was "off". However, Ive just fitted a set of 18" x 8.5 rims and new tyres and the car really feels like new, its like driving on silk! Even with the roof off, its just as smooth. So if any of the Aero owners on-site have this problem, its worth while having a look at your tyres as a possible source of the dreaded shake with the roof off. It certainly has worked for me! Rgds Georigg i have 275/40/18rear and 235/40/18 front japanense rims, came on car from japan, and mine shakes like a good un when the roofs off, i find i get used to it after a few miles anyway. my wheels are in a big need of new front tyres(gone on the inside,tracking!) and the balance is shot to, will sort it soon. Edited July 25, 2008 by supraGZaerotop (see edit history) Quote Link to comment Share on other sites More sharing options...
gordy07 Posted July 25, 2008 Share Posted July 25, 2008 wierd, my roof never shakes. and certainly not with roof off. You sure you are tightening it up properly with a proper hex key spanner thingy? Not the roof mate just general flexing of the car;) Quote Link to comment Share on other sites More sharing options...
extendor Posted July 25, 2008 Share Posted July 25, 2008 Interesting read. Just about to look at my first Aerotop and drive it. At least I wont walk away thinking its knackered now. Many thanks. Quote Link to comment Share on other sites More sharing options...
Aero-M Posted July 25, 2008 Share Posted July 25, 2008 a couple of times i have pulled up on my drive and gone to put the roof on, and it won't fit. couldn't beleive just how much the chassis flex's. Quote Link to comment Share on other sites More sharing options...
dangerous brain Posted July 25, 2008 Share Posted July 25, 2008 Yeah thats a bit scary that is. The do-luck centre brace (I assume other people make them but do-luck is the only one I know of) and a rear brace will stiffen things up a bit. Only way to 100% alleviate the issue is do like the yanks and weld it shut or fit a hefty roll cage. Quote Link to comment Share on other sites More sharing options...
tDR Posted July 25, 2008 Share Posted July 25, 2008 Mycroft. Quote Link to comment Share on other sites More sharing options...
Homer Posted July 25, 2008 Share Posted July 25, 2008 a couple of times i have pulled up on my drive and gone to put the roof on, and it won't fit. couldn't beleive just how much the chassis flex's. Yeah, I was amazed by this after removing the roof when the car was on axle stands. One of the front stands was lower than the other, it sat with a 1inch clearance for days with the roof on, after removing the roof, 5 minutes later one corner had dropped right down to sit on the stand! No way to get the roof back on until it was jacked up again. I'm going to try a test next time its on stands just too see how much it will actually flex It's really shocking just how unstable it is without the roof, no amount of strut bars or under bracing will solve the fact there's no fixed brace between the windscreen and the rear section. Quote Link to comment Share on other sites More sharing options...
extendor Posted July 25, 2008 Share Posted July 25, 2008 Quick question then for the aero owners. When I get the Aero is it Ok to jack them up with the roof off using the standard sill jack. It sounds to me like it will just twist. I also assume you dont try to take the roof off/on with twist in the chassis like with car sat with one wheel on a kerb or similar. Quote Link to comment Share on other sites More sharing options...
Aero-M Posted July 25, 2008 Share Posted July 25, 2008 Quick question then for the aero owners. When I get the Aero is it Ok to jack them up with the roof off using the standard sill jack. It sounds to me like it will just twist. I also assume you dont try to take the roof off/on with twist in the chassis like with car sat with one wheel on a kerb or similar. I would leave it on if I were you. like homer said he's moved a lot on stands. mine only does it if I park on the uneven part of the drive way. the only way to get the roof back in, is to park on the road nice and flat Quote Link to comment Share on other sites More sharing options...
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