Jump to content


Photo

Suspension guru needed. Shorter front control arms?


  • Please log in to reply
48 replies to this topic

#26 axistr

axistr

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 926 posts
  • Location:North west sydney
  • Joined: 19-November 05
Garage View Garage

Posted 03 February 2020 - 07:30 AM

It's not ideal because it leaves you no wiggle-room on the alignment and you still have a huge scrub radius to deal with, which means heavier steering, a tendency toward understeer, and wheel-to-body clearance problems (because the wheel swings in a bigger arc). And adding negative camber further increases positive scrub radius too, making things worse.

 

Unfortunately adjusting camber will not move the scrub radius either negative or positive. Scrub radius can only be moved by rim off set or bending the stub axle and changing the king pin inclination which is defently not the go.   



#27 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 03 February 2020 - 12:10 PM

Really appreciate everyone's thoughts and advice and why i love the forum over the facebook groups of good people and bellends all mixed in together!

I think it will be a case of what's been advised of creeping up on it slowly with a mix of flares, negative camber, offset bushes (which i hadnt heard of before) and then P76 brakes if that doesn't get me enough room.

Ill definitely let you all know how i go in the end.

The car will basically have a set of fancy pants wheels for show etc and then another set of more sensible wheels for driving and cruising etc.

The things we do to ourselves............

Thanks all.



#28 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 03 February 2020 - 02:03 PM

The offset bushings effectively do the same thing as shortening the control arm, because they move the pivot point (making a shorter distance between the inner pivot and the outer ball joint). Not as extreme as chopping 20mm out of the arms but.

 

Anything you can do to reduce the scrub radius is the best starting point - brake/hub and wheel offset in particular. After that if you're close you can look at improving clearance with negative camber and physical alterations.



#29 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 03 February 2020 - 07:16 PM

Update for those interested. I spoke to the guys at Hoppers Stoppers today who were incredibly helpful and willing to go the extra mile.
They said the P76 option is doable and will work and they sell the bearing kit that is required. However they also suggested another alternative they do themselves which is a hub they machine up themselves attached to a custom rotor. Probably slightly more than the p76 route but a better quality outcome and gives me better caliper options. They are looking into if they can do a 320mm rotor for me or not. But the best part is a 14mm reduction on both sides to bring the wheels in. It’s a great outcome and that’s the way I’ll go on top of widening my front flares which should solve my problem and give me plenty to play with to get the handling and steering pretty close.
Once I know more I’ll keep you all updated.

#30 claysummers

claysummers

    Forum Fan

  • Members
  • PipPipPipPip
  • 437 posts
  • Name:Clay
  • Location:Willunga
  • Car:186 FB Ute, 3.3 EK sedan
  • Joined: 13-December 18

Posted 03 February 2020 - 10:34 PM




Sent from my iPad using Tapatalk

#31 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 04 February 2020 - 05:46 AM

Excellent, that's definitely a good way to go about it. Given the offset I imagine your custom wheels will have plenty of brake clearance to make it possible too.



#32 Heath

Heath

    I like cars.

  • Members
  • PipPipPipPipPipPipPip
  • 17,000 posts
  • Name:Heath
  • Location:South Eastern Suburbs, Melbourne
  • Joined: 07-November 05
Garage View Garage

Posted 04 February 2020 - 03:18 PM

How much tyre is there on these front wheels?

 

You can make dramatic changes to what you can get away with by changing tyres. Like I've got a car with 245's on 8"s, and at the other end of the spectrom, I have another car with 195's on 9"s, for example. Those differences are huge. There is of course an aesthetic factor there as well that needs to be considered.

 

Curiously, what are the specs on the front wheels? 10" wide -36 offset or something? 

 

Certainly custom hubs is pretty high on the list of what I'd be doing (a lot higher than changing arm length!). But I would get the car sitting at a good height with your desired camber settings and playing with tyres before anything else.



#33 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 04 February 2020 - 03:34 PM

Hi mate. Wheels are 18 x 9 inch with a 4 inch backspace. (I should’ve gone 4.5 inch backspace)
Tyres are 245/35/18 I can go back to 235 to help a little bit that won’t help a huge amount as wheel lip is still going to be there.
I am doing basically what you just said. Tyres, negative camber and flares widening then if that still leaves me short of where I need to be the custom hub/ rotor set up will solve the rest of the problem.
I guess I will get there eventually. Hopefully!

#34 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 05 February 2020 - 04:47 AM

That should be do-able, I have 17x9 with roughly 5" backspace and 255/40 tyres:

P1000607.jpg

 

The backspace difference less your narrower tyre width adds up to your 20mm (per side) wider at the tyre edge so if you can find that it should clear. I had to clearance the flares a little and take a bit of a chunk out of the firewall (that scrub radius we've all been talking about) but it has full clearance now and I've got camber quite minimal at about -0.6 degrees, and the flares are nothing special.

 

Tyre size will help a lot when it comes to clearance, both width and diameter. 235/35/18 is not only (again, theoretically) 10mm narrower but also 5mm smaller diameter than my 255/40/17. Going to a 235/35/18 reduces both again, and the corners of the tyre are where the clearance issues are.



#35 myss427

myss427

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 1,531 posts
  • Location:Canberra
  • Car:427 hatch, CV8 Monaro, Ve SSV ute. Was part owner A9X sedan until he sold it without telling me!
  • Joined: 17-November 05
Garage View Garage

Posted 05 February 2020 - 08:22 AM

Hi Adrian,

Not sure how your Billets are made, but mine are basically a 2 piece construction, a billet center & a rolled outer band, welded at the rear.

Have you considered getting the weld machined out, center moved out to your required offset & re-welded? Worst case you might need new outer bands.....

 

Dragway in Melbourne can do this for you, not too dear either!



#36 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 06 February 2020 - 09:40 AM

Dragway in Melbourne can do this for you, not too dear either!

Thanks Brett. i am going to give them a call and see if it is doable with the wheels i have and what the cost is.

It could be another option to look into, cost dependent.



#37 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 06 February 2020 - 09:43 AM

That should be do-able, I have 17x9 with roughly 5" backspace and 255/40 tyres:

P1000607.jpg

 

The backspace difference less your narrower tyre width adds up to your 20mm (per side) wider at the tyre edge so if you can find that it should clear. I had to clearance the flares a little and take a bit of a chunk out of the firewall (that scrub radius we've all been talking about) but it has full clearance now and I've got camber quite minimal at about -0.6 degrees, and the flares are nothing special.

 

Tyre size will help a lot when it comes to clearance, both width and diameter. 235/35/18 is not only (again, theoretically) 10mm narrower but also 5mm smaller diameter than my 255/40/17. Going to a 235/35/18 reduces both again, and the corners of the tyre are where the clearance issues are.

Thanks mate. All good info from someone who has been there and done that.

 

I am definitely going to look at changing the tyres as that will buy me a little bit of room. Although i can't go any less than 235, but 10mm give or take will help.

 

Without question it is the one inch difference in backspace between my wheels and yours that makes all the difference. I just have to work out how to "find" it now in other ways. Hindsight is a marvelous thing!



#38 rexy

rexy

    Lotsa Posts!

  • Members
  • PipPipPipPipPipPip
  • 2,606 posts
  • Name:Rexy
  • Location:Melbourne
  • Car:Kia grand carnival!!!
  • Joined: 03-November 09

Posted 06 February 2020 - 04:30 PM

17 x 8.5 with 5.25 inch backspace. 234/40/17.

 

Attached File  3339B25D-8EF9-4563-A38D-52FDFEBBDB85.jpeg   88.02K   3 downloads

 

Attached File  8CC438E7-133D-4E22-AC6A-C6EC708AA527.jpeg   369.79K   4 downloads

 

 

 



#39 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 07 February 2020 - 12:17 PM

Hi Adrian,

Not sure how your Billets are made, but mine are basically a 2 piece construction, a billet center & a rolled outer band, welded at the rear.

Have you considered getting the weld machined out, center moved out to your required offset & re-welded? Worst case you might need new outer bands.....

Mine are made the same way and this is a great suggestion. I have spoken to dragway in Melbourne and they are getting back to me.

 

This could definitely be an option for me instead of re doing brakes and or suspension.

 

Thanks for the idea, i appreciate it.



#40 Heath

Heath

    I like cars.

  • Members
  • PipPipPipPipPipPipPip
  • 17,000 posts
  • Name:Heath
  • Location:South Eastern Suburbs, Melbourne
  • Joined: 07-November 05
Garage View Garage

Posted 07 February 2020 - 12:42 PM

Backspace measurements are the WORST thing to try and compare between. So much back calculating.

 

18"s on the front are bit of a shit idea anyway FYI, than -1" is extra shit, but you could go to a 225 or something and might start getting away with it. The small tyre profile hinders your ability to adjust with tyre width, and the huge diameter just hurts in every way.

 

Wheel width is irrelevant (or you can use "backspace" if you want to use shit measurements) until your wheel start fouling on things like suspension, only tyre width is relevant.

 

Adrian's wheels are 18x9 -1" offset

 

76lxhatch is 17x9" with 0 offset. 

 

Rexy's are 17x8.5" +.75" offset

 

That actually tells you where the tyre sits on each, assuming the same hub face position. That's a range of 1.75" which is loads.

 

Only the white car actually fits its wheels well here. Your wheels are 1" from where they should be in offset. The blue car pretty much doesn't need the flares, and you need a hell of a lot of camber, tyre stretch, hub modification, or flare modification to get it to work.



#41 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 07 February 2020 - 08:11 PM

Backspace measurements are the WORST thing to try and compare between.

I kind of agree but it does offer an absolute measurement for clearance purposes which an offset doesn't due to variations in rim sizes and designs.

76lxhatch is 17x9" with 0 offset.

Actually they're +3mm which is why I said 'roughly' but near enough.
 


At the end of the day if you have two piece wheels after all then changing them is the best solution! You can use more standard suspension and brake parts and improve both scrub radius and clearance.

#42 mugginz

mugginz

    Forum Fan

  • Members
  • PipPipPipPip
  • 311 posts
  • Name:Greg
  • Location:Geelong
  • Car:LH Torana
  • Joined: 27-November 13

Posted 07 February 2020 - 10:39 PM

Actually they're +3mm which is why I said 'roughly' but near enough.

How do you find the steering performance with that kind of scrub radius? Any trouble with tram-lining, kick back at the steering wheel, etc?

#43 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 08 February 2020 - 05:24 AM

I think you'd be surprised at what offsets some of the commonly used wheels are, aftermarket 7" and 8" wheels in HQ pattern are often zero or even small negative offset (e.g. the old Cragar S/S 15x8" were -6mm), going wider can actually give you options with more positive offset provided you clear the inside. So the scrub radius isn't perfect by any means but its not bad at all. No doubt it could be better when compared with a more modern vehicle but I don't notice any ill effects, there is some transmission of road noise and features but the firm suspension is more to blame for that.

 

In some ways its not really a fair comparison because I have power steering and some tweaks to the front end to allow me to run around 6.5 degrees of caster with only -0.6 degrees camber (static), which all helps. After many years of refinement its not a bad package and handles reasonably well.



#44 rexy

rexy

    Lotsa Posts!

  • Members
  • PipPipPipPipPipPip
  • 2,606 posts
  • Name:Rexy
  • Location:Melbourne
  • Car:Kia grand carnival!!!
  • Joined: 03-November 09

Posted 08 February 2020 - 01:49 PM

Backspace is a very useful measurement in these older cars, especially if you are dealing with original diameter wheels. Any more than 4.25 inch backspace on the front of a LH/ LX and you are likely to have clearance issues with the top ball joint.

Going to a bigger diameter wheel allows a lot bigger tyre because you can fit a bigger backspace wheel and still clear the outer guard.



#45 Uncle Chop Chop

Uncle Chop Chop

    Grumpy old man

  • Members
  • PipPipPipPipPip
  • 1,204 posts
  • Name:John
  • Location:Vic
  • Joined: 19-November 12

Posted 08 February 2020 - 05:23 PM

Hi mate. Wheels are 18 x 9 inch with a 4 inch backspace. (I should’ve gone 4.5 inch backspace)
Tyres are 245/35/18 I can go back to 235 to help a little bit that won’t help a huge amount as wheel lip is still going to be there.
I am doing basically what you just said. Tyres, negative camber and flares widening then if that still leaves me short of where I need to be the custom hub/ rotor set up will solve the rest of the problem.
I guess I will get there eventually. Hopefully!


Legally, a 225 is an allowed fitment on a 9" wide wheel, provided it is a 60 profile or smaller. A 225/40R18 is about 8 mm smaller in overall diameter than a 245/35R18. Just a thought.



#46 UCSLE

UCSLE

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 540 posts
  • Name:troy
  • Location:perth
  • Car:Goggomobil
  • Joined: 23-June 09

Posted 08 February 2020 - 10:59 PM

wheel diameter changes the scrub angle too , not by much roughly about 2-3mm decrease for every inch in wheel diameter over stock .

so the larger wheels will help a little with that .

 

drop stubs is another thing that can change scrub

 

I very much doubt you chop 20mm out the arms without the brakes hitting the k-frame big time



#47 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 6,657 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 09 February 2020 - 07:18 AM

Wheel diameter alone does nothing, you have to change the rolling diameter which includes tyres, and you generally reduce tyre profile as wheel size increases to minimise changes to rolling diameter. Scrub radius (not angle) is affected by raising or lowering the steering axis in relation to the wheel, which is why drop stubs also have an effect (in this case making it worse).



#48 adrianh08

adrianh08

    Forum Member

  • Members
  • PipPipPip
  • 214 posts
  • Name:Adrian Haynes
  • Location:Canberra
  • Car:1974 LH
  • Joined: 24-June 10

Posted 14 February 2020 - 12:12 PM

Quick update for those playing along........

Eric at Hoppers Stoppers has been an enormous help and between his efforts and my research i am going to be getting a custom set of hubs made attached to 320mm BMW discs that will bring my wheels in about 12-13mm each side (give or take as i don't have them on the car yet)

This is similar in theory to the old P76 rotor idea but i needed to still go 320mm as much as possible and these do not exist. 

With a lot of searching for the specific height and width disc i needed we found a few options.

I have already attacked my front flares making my own set of wider flares similar to what you can buy for the rear flares off the shelf, just not that wide though.

Anyone who has played with fibreglass, especially trying to widen their own flares will know how much fun that process was.  

So basically once the custom brake set up is made and on the car, on top of the custom flares ive done i should be very close to spot on track wise and it has already been dummy tested on a torana and it does not foul on anything.

So based on my maths (which should be better than my ability to get offset spot on from the start!) i should be very close to spot on and i still have the option of changing the tyres which can buy me another 5mm or so.

I will eventually share some photos once i've had a win.

Assuming i do of course! 



#49 neglectedtorana

neglectedtorana

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 612 posts
  • Name:Tom
  • Location:Sydney
  • Car:LX Torana Sunbird
  • Joined: 06-March 12

Posted 14 February 2020 - 09:46 PM

Good luck Adrian, hope it's a success




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users