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GT6 mk3 Rotoflex anti roll bar - 7/8” or not?


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I was about to fit a 7/8” arb to my rotoflex mk3 as I assumed that all of the small chassis arb’s are interchangeable, in terms of fitting. I know that this combination is frowned upon but I wanted to try it anyway. As of about three hours ago I discovered that the u-bolts are bigger and don’t fit so now, with the extra work considered, am I wasting my time? If so, I have a 7/8”  setup to sell/swap for an 11/16” setup. 

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Yes, the u clamps are bigger, but the holes inthe mounts can be redrilled easily enough, or even filed.

However, a bigger front ARB will induce more understeer. You probably have enough of that already....

How does it drive without a front ARB? I found with stiffer springs on my Herald steering was fantastic without an ARB. If you are thinking of thicker, you really should try without too....

(curveball here. Not sure if the smaller ARB bushes could be drilled out so the std clamps could be used? If you have the old ones it may be worth a look)

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as an AR bar does little till there is any body roll its hard for me to grasp the extra 3/16" makes such a vast effect on handling, 

the supposed stiffer bar ( is it actually stiffer or just thicker to be more stable and resist setting)  will give less toe in on turns than a 

and make it feel understeer, ,  the whole geometry settings have more detriment to handling than an AR bar 

i had a courier spring and thick bar and she  ( Vit6) was very flat  but  on rails compared to the std set up . 

 from what i see ??    the 217033 7/8" was introduced across many of the range ,  later  not just swinger springs 

 

 

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9 hours ago, clive said:

Yes, the u clamps are bigger, but the holes inthe mounts can be redrilled easily enough, or even filed.

However, a bigger front ARB will induce more understeer. You probably have enough of that already....

How does it drive without a front ARB? I found with stiffer springs on my Herald steering was fantastic without an ARB. If you are thinking of thicker, you really should try without too....

(curveball here. Not sure if the smaller ARB bushes could be drilled out so the std clamps could be used? If you have the old ones it may be worth a look)

 

9 hours ago, clive said:

Yes, the u clamps are bigger, but the holes inthe mounts can be redrilled easily enough, or even filed.

However, a bigger front ARB will induce more understeer. You probably have enough of that already....

How does it drive without a front ARB? I found with stiffer springs on my Herald steering was fantastic without an ARB. If you are thinking of thicker, you really should try without too....

(curveball here. Not sure if the smaller ARB bushes could be drilled out so the std clamps could be used? If you have the old ones it may be worth a look)

Hi Clive, I’ve not driven it yet. I got this arb a while ago as it was cheap, I couldn’t find a small one and, I wanted to get the car built. I knew about the understeer issue but not that the parts wouldn’t fit. 

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6 hours ago, Ian Foster said:

I have reverted to an 11/16" bar after using a 7/8" bar for many years on my Rotoflex GT6 Mk2.

Without going into chapter and verse about why and when and who (me obviously) I confirm that the smaller bar it is much, much better!

Ian

Thank you Ian. I shall get an 11/16” bar. According to CC website, the 11/16” bar is fitted to all of these, as per the image. Is this correct? 

E243A3BD-CAAE-4C1D-8282-5A4E58120174.png

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32 minutes ago, Adrian Saunders said:

 According to CC website, the 11/16” bar is fitted to all of these, as per the image. Is this correct?

AFAIK, the 11/16" was correct for all swing axle and Rotoflex, the 7/8" was only on the swing spring cars. Pete may be right about "later" cars also having a 7/8" one but those are either a lot heavier (2000 saloon) or have a live rear axle (Dolomite).

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I  would agree the     207093   11/16" bar is not available all superceeded by the     217033    7/8"

Canley may have updated the part number link but on 13/60 it only lists 217033   there no  ref to the small one

You may find a second hand one 

Heres some clues on roll  stiffness to  chew over http://auskellian.com/paul/links_files/springs.htm

There was a  previous post  a while back about the small bar being designed with a set in in it as they  all show  up as twisted,  the 7/8  is always supplied  as flat as you would  expect

Pete

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We have touched on lube for bushes with various thread drifts (!!). When I spoke to one of the Polybush team at the NEC restoration show in March, she said only use a smear of washing up liquid to prevent the formation of a grinding paste. Other here have used numerous other rubber greases, so its try it out and hope for the best.  What ever 'slips' your boat so to speak. I mentioned to her that R*****s had tried to sell me some sort of grease when I ordered my Polybushes and she went over to their stand to sort them out. I made a hasty exit!!!

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5 hours ago, Badwolf said:

We have touched on lube for bushes with various thread drifts (!!). When I spoke to one of the Polybush team at the NEC restoration show in March, she said only use a smear of washing up liquid to prevent the formation of a grinding paste. Other here have used numerous other rubber greases, so its try it out and hope for the best.  What ever 'slips' your boat so to speak. I mentioned to her that R*****s had tried to sell me some sort of grease when I ordered my Polybushes and she went over to their stand to sort them out. I made a hasty exit!!!

I’ve not considered that before. Has anyone seen significant wear in the bush region on standard or Polybush installations? 

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 laal tyres, no very grippy, esp wid 2 degs positive camber

pottering aboot speeds / driving, then small bar fine

 

v stickty  tyres, or bigger  better tyres will result in moer roll,

What happens is yer tyres then bite,

this then causes grip induced roll, pain in the butt wid 60 TW tyres

but will also give too much roll on ordinary road tyres if gon t, 205s an 2 deg neg camber

 Alott is dependant on  yer tyres, can be alott of roll like 30 sih  degs roll on a hard 70-90 deg corner

 

Im running 1200LB springs up front  wid a 7/8th bar to compesate,

and a an adjustable  front TR6 bar ont rear, t even it up a wee bit

tried the wee bar on fronts ,but roll was still alott.

 

horses for courses summary

pottering / normal drive, oe  wee roll bar  quite adequate

honk,n on, bigger tyres, stickee tyres , neg camber, then a biggggg no no

 

 

M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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  • 3 months later...

Good morning Dick, I collected the ARB yesterday, thank you very much. I forgot to get the correct mounts and Canley’s are closed this week. Waiting for delivery from James Paddock now!

Whilst talking to Lesley and her husband Roger yesterday, we realised that my two boys sat in Lesley’s Stag at Solihull “Fun in the Park” a couple of years ago. Picture attached. We plan to visit the event this year. It’s only small but there are some great cars there. Hopefully my GT6 one day! 

B25685D1-E8CE-4ADD-ADC7-29455CE00D86.jpeg

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This is an interesting point.   Some say ..... As La Clarkson used to , that Triumph fitted biased ARBs intentionally, as their sports cars would usually have a solo driver (sad idea).   Others say this is nonsense, cornets go both ways, we're not driving on American ovals.

Gaydon may hold the answer, but I have yet to get there and do the research in their records.

John

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On 06/09/2019 at 15:22, Pete Lewis said:

one asks why would you induce a twist, ...........to compensate road camber ?   or what , makes no sense the LHD has the same AR bar  so that doesn't add up 

None of the workshop manuals or other reference books mention any direction of fitting, which would be important if any kind of bend was meant to be there, otherwise fitting it incorrectly is bound to have an adverse effect on handling.

Anyone selling new items - Jigsaw Racing for one - show a completely flat bar.

roll.jpg.683fc99c923c212c5fe354e165ba62f8.jpg

 

 

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in all my years the only time there's a designed quirk is for a race circuit , road going camber and antiroll are all neutral

if cars had odd spring heights to compensate for road camber then the AR would need to copy , but our small chassis are not in that league.

flat  ....   just   has to be flat  

pete

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