FW: [MarcosManiacs] RE:Wheel backspace
2003-05-15 by pauldransfield@iname.com
I did it
again. The 'backspace less than 35mm' in the second paragraph should have said
'offset less that 35mm'.
-----Original Message-----
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From: pauldransfield@...
[mailto:pauldransfield@...]
Sent: May 15, 2003 3:00 PM
To: MarcosManiacs@yahoogroups.com
Subject: [MarcosManiacs] RE:Wheel backspace
Sent: May 15, 2003 3:00 PM
To: MarcosManiacs@yahoogroups.com
Subject: [MarcosManiacs] RE:Wheel backspace
Hi Don,
This is a resend and correction from an earlier
post that seems to have been lost in hyperspace. I used backspace when I mean
offset at the end of the second paragraph.
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Some
confusion for some people comes from the fact that rim width is measured
across the inner surfaces of the wheel (where the tire sits), and backspace is
measured from the hub mating surface to the distant edge of the inner rim
lip. Your calculations below would
imply that a 5.5" rim is actually 6.5" wide, and a 7" rim is actually 8" wide.
I'll go along
with that and your rationale regarding backspace preference for a 7" wheel.
Unfortunately, I haven't been able to locate any wheels with a 4 x 4.25 PCD and
a backspace less than 35mm. They must be out there somewhere so I've sent an
email to a large Canadian distributor of tires and wheels requesting information
on 16" and 17" wheels with an offset of less than 15mm. If they come up with anything, I'll let you know. And
if you've found/find any yourself, I'd appreciate you letting me
know.
By the way, in your email on this subject on 25th April, you
said the original alloys had a positive offset of .25". Shouldn't that be
negative .25"?
Regards,
Paul
Dransfield
3 litre
Volvo
-----Original Message-----
From: Don Lattimer [mailto:donlattimer@...]
Sent: May 15, 2003 12:23 PM
To: MarcosManiacs@yahoogroups.com
Subject: Re: {SPAM} [MarcosManiacs] Wheel backspacePaul,My $.02. With the current wheel (13"x5.5") the backspace is 3" which leaves 3.5" to the outside edge. With a 15x7 wheel with a 4" backspace (which Mike seems to prefer with his 13" wheels), the backspace is increased by 1" and the distance to the outer edge (frontspace?) is increased by 1/2" to 4". I wouldn't want the wheel/tire to extend much further than it is now or it will hit the fender (wing?) during driving.If the 13" fits fine with a 4" backspace then I would imagine the 15" would because it would clear the brake caliper easily. Then you've got lock-to-lock to worry about.I'm leaning toward a 15x7 wheel with a 4" backspace (0 offset) but would love to try one before committing to a purchase.Don Lattimer#3m5759----- Original Message -----From: pauldransfield@...Sent: Thursday, May 15, 2003 8:51 AMSubject: {SPAM} [MarcosManiacs] Wheel backspaceHi Mike,You seem to have played around with this issue in the past. Did you do any investigation into the backspace requirement for larger wheels? Do you happen to know the maximum practical backspace for a 16" or 17" wheel?Regards,Paul-----Original Message-----
From: Mike Denman [mailto:mikedenman@...]
Sent: May 6, 2003 9:55 AM
To: MarcosManiacs@yahoogroups.com
Subject: Re: [MarcosManiacs] 100 Members !!Hi group,Actually, I have 13 inch Panasport wheels, 7 inches wide (as I recall... I can check if someone really needs to know) with 4 1/4 backspacing. 4 1/4 back spacing is the maximum that will clear everything with 13 inch wheels.The first thing that will hit ( with 13 inch wheels) is the upper "A" arm on the front suspension. If I were to order the same wheels again I think I would go with a 4 inch back spacing to give a little more clearance. Panasport can do any 4 bolt wheel pattern from what I understand. 14 inch wheels weigh more and give you more unsprung weight which is a bad thing. My conversion from wire wheels to Panasports resulted in a savings of almost 60 pounds which made a huge difference in the handling. It also has a pretty big effect on the power to weight ratio since the car only weighs 1780 pounds. The 3 3/4 bolt pattern is correct for the Triumph hubs and the Cortina Rear end was stock at 4 1/4 inches. The Marcos factory would re-drill the Cortina rear axles to the 3 3/4 inch pattern. Unfortunately, the 3 3/4 inch pattern with Triumph studs is not the strongest assembly around. One way around this problem is to fit aluminum hubs in the front drilled to the 4 1/4 pattern and use the stock 4 1/4 Cortina rear axles. The aluminum hubs are expensive but available from Dave Bean Engineering in California. The aluminum hubs are also quite a bit lighter saving almost 3 lbs per front wheel (which is a good thing). I ended up with Toyo RA-1 DOT legal race tires on the recommendation from Roger Krause who sells Vintage race tires as well as modern race tires. I had originally set out to buy Hoosiers which are basically a DOT legal race slick figuring that I didn't ever drive in the rain so they shouldn't be a problem. So far I have had two track days in the rain and got caught on two long trips in the rain. The Toyo tires aren't great in the rain (as I found out at Thunderhill last weekend) but at least they aren't dangerous. In the dry they are great. They have a wear index of 40. (Pure race tires have an wear index of basically 0. My Yokohama AVS "performance tires" had a wear index of 160. So the lower the wear index the better the tire will grip... but the lower the wear index the quicker the tires will wear out.) However, tires get hard as they get old so wearing out the tires is not all bad. When I took the Yokohama AVS off the car they looked like new even though they were 3 years old (not a good thing). Because the Marcos is so light even the Toyo tires will probably last me a couple of years.Mike DenmanChassis #4079----- Original Message -----From: markwoof92@aol.comSent: Monday, May 05, 2003 9:32 PMSubject: Re: [MarcosManiacs] 100 Members !!Paul,
After squeeling and sliding around the Thunderhill track on my 195/70/13s with the nice folks of the Volvo Club of America,I too am motivated to upgrade my wheel and tire setup and I did bit of poking around a bit and was told that Panastort rims might be of use to look into ,they are not cheap (about $250 each or so) but less costly than a new set of hubs and less expencive rims.I was told that they can drill the wheels at the factory to fit any bolt pattern.
Mike Denman hase a set of Panasports(14 inchers) so might want to check with him to get his oppinion.
A while back Don Lattimer was looking in to this very same subject.
Don?Any progress?
Regards,
Mark Petrinovich
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