Can anyone tell me what offset they are using, on the front end, with alloy (not wire) wheels, and what rim width and tyre width? Also whether you had to limit the steering lock to avoid the wheels/tyres catching on the bodywork?
For your information, I am planning to use 5.5"x13" wheels with 175/60 tyres, but I don't know what offset to order in order to ideally avoid, and at worst minimise, contact with bodywork issues.
Wheel Offset
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Westfield 129
- Posts: 867
- Joined: Sat Jun 04, 2011 4:20 am
Re: Wheel Offset
5.5X13 wheels will be a bit wide in front unless you have a backside space of around 4 1/4" (the 5" rim has a 3 7/8" backside space, plus 1/4" to handle the rim width increase and keep the center of the tire in the right place). This will keep the proper geometry but there is no combination that doesn't touch the clam on at least one side of the front clamshell at full lock. You will still need a rack stop if that bothers you. The available rims in 5.5" will all sit about 3/8" outside the usual 5" wide common Minilite type cast Midget application wheel, which will make your wheel contact problem much worse, changing the scrub radius, and making a steering rack stop mandatory.
Best to use a 5" wide rim, backside space of 3 7/8" and a 165/13 or a 185/70/13 and stay away from the low profile tires. They don't help the handling, or the ride.
This will keep the rim center in the right place for the steering geometry. Any of the usual Minitor or other Minilite form cast wheels for Midget will be of this measurement. Any of the wheel dealers can give you the backside spacing measurement.
I am not aware of a 5.5" alloy rim that is within 3/8" of the required backside measurement in an off the shelf application. Most of the 5.5" rims put the extra half inch all on the outside for a track increase, or to give the appearance of a wider rim. I have been trying to find an off the shelf 5.5" alloy rim that will work in front, but so far, no joy. The likely candidate will be a wheel designed for a front drive vehicle, with a very deep backside spacing measurement, and cast in magnesium. It also has to look period. The search continues.
Best to use a 5" wide rim, backside space of 3 7/8" and a 165/13 or a 185/70/13 and stay away from the low profile tires. They don't help the handling, or the ride.
This will keep the rim center in the right place for the steering geometry. Any of the usual Minitor or other Minilite form cast wheels for Midget will be of this measurement. Any of the wheel dealers can give you the backside spacing measurement.
I am not aware of a 5.5" alloy rim that is within 3/8" of the required backside measurement in an off the shelf application. Most of the 5.5" rims put the extra half inch all on the outside for a track increase, or to give the appearance of a wider rim. I have been trying to find an off the shelf 5.5" alloy rim that will work in front, but so far, no joy. The likely candidate will be a wheel designed for a front drive vehicle, with a very deep backside spacing measurement, and cast in magnesium. It also has to look period. The search continues.
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Westfield 129
- Posts: 867
- Joined: Sat Jun 04, 2011 4:20 am
Re: Wheel Offset
20~25 mm on a 13X5" rim.
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StephenH
- Posts: 25
- Joined: Sat Oct 31, 2015 8:28 pm
Re: Wheel Offset
If ET20mm is the "correct" offset on a 5"x13" rim, then the 5.5"x13" JBW Classic Minilight replica is the "correct" offset for a 5.5" rim despite what you say, because it has ET25mm. offset which by my reckoning puts most (5mm.) of the increased width (6.35mm.) on the inside, not the outside, of the wheel, and only a bit (1.35mm.) on the outside, so it increases the track by a trivial 2.7mm or thereabouts.
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Westfield 129
- Posts: 867
- Joined: Sat Jun 04, 2011 4:20 am
Re: Wheel Offset
Ok, but the only way to really check this is to get the backside spacing. If the number is near 4 1/8", it will work and the car will steer beautifully.
FYI: The total increase in rim width is more like 12.7 mm (.5"), of which only 5mm is in the inside and 7.7 on the outside, using the offset to make that determination, rather than the backside space, which is where the real (measurable on the car) change would be. Its' a all a guess. The reality is that neither of us know the real change in rim position relative to the car without the backside spacing. The rim is going to be wider on the car than you estimate. Only the backside space will tell us how much.
The actual difference in track will be more like 15.4mm (.6")... 2 X 7.7mm (plus the material thickness, say 4mm, which is a bit different than your measurement of 2.7 mm track increase. In other words, there is no free lunch. You are going to get the rim width increase, and then some, moving the wheel closer to the body work. Half an inch is a lot when you are pressing the tires into the fiberglass.
So, again, seeing the backside spacing will tell you more than the offset when it comes to an actual fit.
Yes, there are W11s using this wheel. I know as I compared front track measurments with a couple of owners in the UK, and found that both of my cars (alloy and wire wheels) were about half an inch narrower, than their alloy center track measurements.
I don't see an advantage for you here, other than the low price of the wheels and the extra half inch of width, which is more helpful in the back then the front.
On the surface, it looks pretty good (it would work, but not solve your problem), but... I really want a measurement from the actual rim, and not a phantom measurement from the middle of nowhere. I need to know how the rim's construction fits as well. You would be better off with a rim of the specifications I gave you. You don't need the extra width up front with the tires that will fit on that rim, and work best with the chassis. Also, you save a couple of kilos in rim weight. Wider rims weigh more.
Nevertheless, the wheels are interesting to me, so I Emailed the manufacturer for the hard backside measurement (and some information on some 15" wheels with a Midget PCD, in 5.5 and 6" rim widths. I a sure that I will hear back.
Pricing seems pretty good.
Tires: Stick to a 185/70 or 165, maybe 175/13 and stay away from the lower profile tires to keep predictable (progressive) handling. Low profile tires on these cars make then snappy and unpredictable. They give up all at once, rather than progressively. 'Makes the chassis harder to tune. Taller, 64% or more, is better than shorter (60% or less). I like 70% for the commonly available road tires.
The 15" tires I prefer are bias ply vintage race tires. 4.50L-15 with a 74% aspect ratio and in the rear, a 5.00X15L-15 with a 64% aspect ratio. Very predictable and progressive in breakaway.
FYI: The total increase in rim width is more like 12.7 mm (.5"), of which only 5mm is in the inside and 7.7 on the outside, using the offset to make that determination, rather than the backside space, which is where the real (measurable on the car) change would be. Its' a all a guess. The reality is that neither of us know the real change in rim position relative to the car without the backside spacing. The rim is going to be wider on the car than you estimate. Only the backside space will tell us how much.
The actual difference in track will be more like 15.4mm (.6")... 2 X 7.7mm (plus the material thickness, say 4mm, which is a bit different than your measurement of 2.7 mm track increase. In other words, there is no free lunch. You are going to get the rim width increase, and then some, moving the wheel closer to the body work. Half an inch is a lot when you are pressing the tires into the fiberglass.
So, again, seeing the backside spacing will tell you more than the offset when it comes to an actual fit.
Yes, there are W11s using this wheel. I know as I compared front track measurments with a couple of owners in the UK, and found that both of my cars (alloy and wire wheels) were about half an inch narrower, than their alloy center track measurements.
I don't see an advantage for you here, other than the low price of the wheels and the extra half inch of width, which is more helpful in the back then the front.
On the surface, it looks pretty good (it would work, but not solve your problem), but... I really want a measurement from the actual rim, and not a phantom measurement from the middle of nowhere. I need to know how the rim's construction fits as well. You would be better off with a rim of the specifications I gave you. You don't need the extra width up front with the tires that will fit on that rim, and work best with the chassis. Also, you save a couple of kilos in rim weight. Wider rims weigh more.
Nevertheless, the wheels are interesting to me, so I Emailed the manufacturer for the hard backside measurement (and some information on some 15" wheels with a Midget PCD, in 5.5 and 6" rim widths. I a sure that I will hear back.
Pricing seems pretty good.
Tires: Stick to a 185/70 or 165, maybe 175/13 and stay away from the lower profile tires to keep predictable (progressive) handling. Low profile tires on these cars make then snappy and unpredictable. They give up all at once, rather than progressively. 'Makes the chassis harder to tune. Taller, 64% or more, is better than shorter (60% or less). I like 70% for the commonly available road tires.
The 15" tires I prefer are bias ply vintage race tires. 4.50L-15 with a 74% aspect ratio and in the rear, a 5.00X15L-15 with a 64% aspect ratio. Very predictable and progressive in breakaway.
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Westfield 129
- Posts: 867
- Joined: Sat Jun 04, 2011 4:20 am
Re: Wheel Offset
Measured backside space on your selected 13X5.5 wheel is 4.2", which will fit perfectly.
You have chosen a good dealer too. They got back to me the same day.
The precise measurements on these wheels is available from the dealer or manufacturer, and is published. 'Available to any "man on the street" who has undertaken building his own car.
You have chosen a good dealer too. They got back to me the same day.
The precise measurements on these wheels is available from the dealer or manufacturer, and is published. 'Available to any "man on the street" who has undertaken building his own car.