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Stock wheel offset  Rating:  Rating
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 Posted: 08-31-2013 06:33 pm
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subwoofer
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The markings on the stock rims seems to suggest that the ET of the stock wheels is roughly 19mm, but measuring (with tyre mounted) seems to suggest ET43 or thereabouts. I am measuring a total width of 237mm and backspacing of 162mm. Given the age of the car, ET43 sounds odd.

What I am really after, is what ET to order for 15x7" rims, will ET20 hit anything, or should I go for ET13 or ET10?

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Joachim

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 Posted: 08-31-2013 07:37 pm
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igdboss
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ET call home.

Couldn't resist -sorry.

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 Posted: 09-01-2013 09:18 am
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subwoofer
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:-)

I have been playing a bit with this one:
http://www.rimsntires.com/specs.jsp

At the moment Ms Jensen is shod with 185/70R13s on stock rims. The calculator seems to suggest that 205/50R15 on 7x15 ET10 rims will achieve the desired effect. Like a lot of older cars I think the track looks a bit narrow on stock wheels but I don't want to go overboard in widening either.

Opinions?

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Joachim

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 Posted: 09-01-2013 08:19 pm
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Art DeKneef
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Do not measure with the tire. Measure the rim only. The 19mm is about what I remember, 0.75". It's been several years since I bought the rims but I believe the measurements we came up with were offset of 0.75" and backspace of 4".

I got some Superlite 15x6 that were made for the Jensen-Healey. They were out of 15x7 otherwise I would have gotten those. The tires I got were 205/50x15. Almost the same height as the 185/70x13 tire.

The car definitely looks better with the wider rims and tires.

All right, I went to the car shed and measured the backspace of a rim. It is just a little over 4".

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 Posted: 09-02-2013 06:06 am
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subwoofer
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What offset does your 6x15s have? It should be stamped on the rim.

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Joachim

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 Posted: 09-04-2013 12:45 am
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Art DeKneef
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Well, I got under the car and the rims are marked "ET 15".

Hope that helps.

Art

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 Posted: 09-04-2013 06:15 am
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subwoofer
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Thanks, it did!

It looks like I'll be ordering ET5, then. Since 6x15 ET15 does not hit anything, neither will 7x15 ET5 - unless of course it is really really tight with the 6x15s.

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Joachim

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 Posted: 09-10-2013 07:18 pm
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gmgiltd
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Hi Joachim,
I got 6x15" from the club store and put 195x55 Pirelli P7 tyres on my GT which are very close in radius to the original. I know the front under tray is different between the Mk 1 and Mk 2/GT but I have a very minor clearance issue on full lock when reversing - something to consider.
Gordon

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 Posted: 09-11-2013 05:48 am
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subwoofer
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Which "corner" of the wheel is problematic? If your wheels are ET15 and any of the inner corners rub, reducing ET will help.

But a slight bit of rubbing at full lock is really just a nuisance, it will in reality only happen at very low speeds while parking - or when you have overcooked it on the track... :-)

Thanks for the heads up!

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Joachim

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 Posted: 09-11-2013 06:10 am
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gmgiltd
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Outside corner - are you going for big brakes? It's more of a nuisance than anything else and something to fix after the FI project.

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 Posted: 09-11-2013 07:19 am
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subwoofer
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The brakes are sitting in boxes in my garage just waiting for me to get my finger out... :-)

You are going fuel injected? I doubt you will regret it. :-) I have a bit of experience with the MS3 system, a bit of a Jekyll & Hyde experience at times.

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Joachim

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 Posted: 09-11-2013 05:11 pm
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gmgiltd
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Did you go for the Hispec kit? Front setup is excellent but the rears need longer studs and 6mm spacers to clear caliper to rim plus a bit of ingenuity with the handbrake particularly the return mechanism. It's more a track than road system and needs careful set up to work properly.
I would go for hydraulic but it's not allowed for the MOT. You also need to take out the half shafts and make up a spacer to compensate for the brake backplate thickness.
For the FI I have gone for Jenvey 48 bodies and a DCA40s ECU, Pico injectors with Sitec pump and filters. Bit of work to do and still trying to source an Excel air box in good condition.
Gordon

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 Posted: 09-11-2013 06:44 pm
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Dakota123
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Same experience with the club wheels and 205-50s, minor rub at full lock. Wasn't even aware for quite a while until I noticed the anti-roll bar was cleaner in one area.

I'll post the rest of my recent FI experience (not much) in my project thread.

Oh, and what is a DCA40s ECU -- I'm not familiar with it?

Last edited on 09-11-2013 06:54 pm by Dakota123

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 Posted: 09-11-2013 06:58 pm
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subwoofer
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gmgiltd wrote:
Did you go for the Hispec kit? Front setup is excellent but the rears need longer studs and 6mm spacers to clear caliper to rim plus a bit of ingenuity with the handbrake particularly the return mechanism. It's more a track than road system and needs careful set up to work properly.

Yup, bought the Hispec kit.

Spacers and studs will have to be looked into, shouldn't be too hard to source anyway. Caliper-to-rim clearance could possibly be different with different ETs too, so I may not need them. Time will show. As for ingenuity; I am a mechanical engineer by training, I hope I can figure something out!

I would go for hydraulic but it's not allowed for the MOT. You also need to take out the half shafts and make up a spacer to compensate for the brake backplate thickness.
For the FI I have gone for Jenvey 48 bodies and a DCA40s ECU, Pico injectors with Sitec pump and filters. Bit of work to do and still trying to source an Excel air box in good condition.
Gordon


This thread seems to be warping a bit, but why 48s? Depending on control algorithm (a good MAF implementation is possibly the only way to properly tame ITBs like that) you may have a hard time tuning your installation. Remember that a 40mm throttle body flows a lot more than a 40mm carb!

Have you rung Mike at Lotusbits? He would be the obvious source for an Excel airbox, it is where I got mine.

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Joachim

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 Posted: 09-11-2013 07:00 pm
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subwoofer
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Dakota123 wrote:
Oh, and what is a DCA40s ECU -- I'm not familiar with it?


I am guessing it is a typo, and that he meant DTA S40 (http://www.dtafast.co.uk/S_40_PRO.htm). Not an uncommon unit this side of the pond.

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Joachim

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 Posted: 09-12-2013 12:47 pm
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gmgiltd
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Sorry about the typo - Joachim provided the right answer and the link to DTA - good bit of kit

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 Posted: 10-09-2013 08:00 pm
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subwoofer
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Picked up the new rims today, will get some tyres for them ASAP! I ordered 7x15" ET05 rims, clearance looks good. No need to space out the rears with the HiSpec brakes either, I can easily get a finger between the spokes and the rear caliper.


Lookin' good!

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Joachim

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 Posted: 02-17-2016 07:05 pm
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dbeliveau74
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Anything more to add?
How is your fender clearance?

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 Posted: 02-18-2016 05:31 am
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subwoofer
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I would probably order ET10 if I were to do it again, at least for the fronts. There is occational rub on the forward inner wing at full lock and bump, it is a matter of millimeters. It typically occurs while reversing out of my drive, where there is a sharp bump right as I have to be at full lock.

Could be that the root cause of the rubbing is that the upper mounts for the crossmember are done. I haven't changed those, basically everything else in the suspension is new.

Looks fantastic at ET05, though!

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 Posted: 02-21-2016 12:03 am
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Esprit2
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I've harvested the following from somewhere on the Internet, and cannot verify it's accuracy. Use at your own risk.

Jensen Healey Wheels.
13 x 5.5 Inch
4 x 4.0" (4 x 101.6 mm) Bolt Circle
0.750" (19.0 mm) ET

All that is measured on a bare rim.

Never try to measure ET / Offset on a mounted tire. If that's what you're doing, your results may not be (probably won't be) accurate.

ET and Offset are not the same thing, so when you read a number for a wheel, be certain you know what it is... ET or Offset. Under certain circumstances, they can produce the same number value, but more often than not, they don't. Especially with older wheels, with stamped steel wheels being the least consistant.

Back in the day, I believe Jensen referred to Offset, as did most of the Britcar manufacturers.

It's important to maintain the relationship between the kingpin axis and the centerline of the tire (ie, scrub radius). Willy-nilly playing with the wheel offset messes with the scrub radius, and can negatively affect steering feel and handling.

A customizer, bling-bling artist will use ET. If it fits in the wheel well and looks good, I'm happy.

An engineer or serious racer will be more concerned about correct suspension geometry, and will use Offset.

Choose your poison.

Regards,
Tim Engel

Last edited on 02-21-2016 12:04 am by Esprit2

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