Uprated ARBs no longer available from Torsion Performance

redrover

redrover

Well-Known Member
I emailed Torsion Performance over the weekend to enquire about the uprated ARBs they used to be produce, and received the following this afternoon:

Afternoon Michael,

Thank you for your email.

We used to do these but the specialist person who made these passed away at Christmas, so at present we are not making these.

Sorry for any inconvenience caused

Kind Regards

Renee & Marie-Claire
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I've dropped them a note back to pass on condolences. I assume this now leaves us without a ready source of uprated ARBs for P6? I wonder if it might be possible to obtain the specs (if written down!) from TP to take to another company? I know various members on here have been involved in sourcing/producing these ARBs in the past. Does anybody have specs / drawing, or know of another shop who could manufacture then to the same spec? I have read various threads which suggest the TP performed very well.

@partviking - perhaps something to notify RP6C members of via DF?

Michael
 
I had mine made by KMac suspension back in the early eighties. It was a one off as I couldn't interest anyone else in getting one...After
discussions with Kevin Mac, we settled on 23mm spring steel bar with the ends machined to fit the standard clamps. After busting about four clamp bolts I went up one size. When I transferred the bar to my new frame years ago (from 1971 frame to 1976) I found the cars top links were located a little further in, necessitating the machined part being extended about 1/4" each end. The 76 frame never understeered to the degree the 71 frame did so I suspect its a factory fix. Kevin did say at the time that if I could get a worthwhile order together he would make a forging die for the end which would work out cheaper

Kevin's point on thickness was that the widest cross section of the normal bar is 22mm point to point and 1mm will give a lot more metal, 0.5mm all round but there is more in the flat surface wedges, going for more will make the cornering harsh and be a pain to keep the clamps tight. Plus you'll cook the shocks on rough road...Only other point, which has been brought up elsewhere, is the machining to hex needs to be done lengthwise so there is no sharp ridge at the transition to round bar.
M
 
I designed and made my own 25mm hex bar a few years ago. I used 4140 hex stock which I machined to fit into the standard ARB clamps on the top arms. I had it hardened to 60-65 HRC and it’s given sterling service on and off the track. Ride is pretty much as before with much better body control. I would say upping tyre pressures to 30 psi help with stopping the sidewalls rolling over.

I can probably get some made up as a batch if we have enough interest (they’ll fit both 4 and 8 cylinder cars). The main cost for production was the spring tempering IIRC.

there’s a pic of old and new together here:
Getting back on the road
 
Mine's a 25mm one, an inch for us imperial chaps and I do remember it transformed the handling instantly.
 
quattro said:
Mine's a 25mm one, an inch for us imperial chaps and I do remember it transformed the handling instantly.
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The originals are 17mm (5/8”) so not sure how much extra you get with the 18.5mm mentioned from Wins. Unless they are using a significantly stiffer alloy.
 
Okay, sounds like there are still options out there. Good to know.

sdibbers said:
The originals are 17mm (5/8”) so not sure how much extra you get with the 18.5mm mentioned from Wins. Unless they are using a significantly stiffer alloy.
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I'd agree with this. I'm looking for something to make a fairly dramatic difference, and the reviews I read (on here) of the TP ones seems to fit that bill.
sdibbers said:
I can probably get some made up as a batch if we have enough interest (they’ll fit both 4 and 8 cylinder cars). The main cost for production was the spring tempering IIRC.
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I'd certainly be happy to put my name down for one of these if there is collective interest. What sort of batch size are you envisaging?
@partviking - perhaps we could canvas for this via DF in conjunction with a note on the end of production at TP?

Michael
 
redrover said:
Okay, sounds like there are still options out there. Good to know.


I'd agree with this. I'm looking for something to make a fairly dramatic difference, and the reviews I read (on here) of the TP ones seems to fit that bill.

I'd certainly be happy to put my name down for one of these if there is collective interest. What sort of batch size are you envisaging?
@partviking - perhaps we could canvas for this via DF in conjunction with a note on the end of production at TP?

Michael
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If we can get orders for 10 I think it would work (I'd be making them as part of my company, Additive Restoration) I'll do some research on costs for tempering the parts, I remember for one being treated five years ago it was $125 for one. If there's enough interest I still have my CAD model and drawings to make them in house.
 
sdibbers said:
If we can get orders for 10 I think it would work (I'd be making them as part of my company, Additive Restoration) I'll do some research on costs for tempering the parts, I remember for one being treated five years ago it was $125 for one. If there's enough interest I still have my CAD model and drawings to make them in house.
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I didn't realise you were stateside. Did you ship over to Blightey years ago? Not sure what the carriage cost would be.
 
redrover said:
I didn't realise you were stateside. Did you ship over to Blightey years ago? Not sure what the carriage cost would be.
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We ship stuff world wide. not had too much of a problem so far. Although long, the ARBs aren't excessively heavy or wide. I reckon we could ship them priority mail for a reasonable sum.
 
If all else fails, don’t forget you can pick up a Peugeot 306 rear bar and machine the ends. Models with the suitable 24mm rear bar are GTi6 phase 1 or HDi.
I got mine for £30 and machining was £60 from memory.
Jim
 
Vern Klukas said:
17 to 18.5 mm, all else considered equal, would be about 9% stiffer.

Yours
Vern
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Hi Vern,

Sorry but it isn't actually, it is much more so. Stiffness or in other words resistance to bending (deflection) for a given shape is based upon what is known as the second moment of area which has units to the fourth power. In the case of a 17mm regular hexagonal bar, each side length will be 8.5mm. The second moment of area is 2825.44mm^4. This is not an area measurement in the normal sense, rather it provides a measure of that cross-sectional shapes' resistance to deflection. With an increase in diameter to 18.5mm the side length becomes 9.25mm. The second moment of area is now 3962.58mm^4. Assuming that Young's modulus (the stress-strain relationship) for both bars is unchanged, then the 18.5mm bar is 40% stiffer. Second moment of area is just one of the parameters that structural engineers will use to assess a member's resistance to deflection.

Ron.
 
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I bought a 25.5mm front ARB from Classeparts back in 2007.
I'm embarrassed to admit I can't follow Ron's math! How much stiffer is my uprated bar in comparison with a standard 17mm bar?
 
mrtask said:
I bought a 25.5mm front ARB from Classeparts back in 2007.
I'm embarrassed to admit I can't follow Ron's math! How much stiffer is my uprated bar in comparison with a standard 17mm bar?
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I have the Torsion one at 24mm and that's pretty stiff... I went to Torsion themselves 3 years ago and I got a tour of their machine shop. Very impressive very interesting. The are very proud of the bespoke work they do and I'm sad to hear he passed on.

It's not quite that equation though because the end of the bar is thinner and will consequently distort more than the center of the bar. With good spring steel this will likely be fine but obviously it put higher stresses on the ends.
 
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