Alloy wheels for Javelin/Jupiter, possibly others

[Srenner]

Well, it seems there has been a bit of work already done. I thought we were still in the jibber jabber stage!

IMHO, taper bearings are the correct step in updating the hub performance. Sure, they might cost more up front, but they are superior in all aspects when it comes to suspension design. We need to move away from the old taper bearing replacements, as they are hugely expensive. Last time I checked here in the US, it was over $300 per side.

I will be talking to the owner of Centric brakes today. They manufacture a large range of aftermarket performance brakes and he owns several Porsche 356 variants, so he has begun alloy brake drum production for those. I will take a front and rear drum for him to have a look.

Cheers,
Scott

[p.p.]

its also for "Rhowina" - that mean's NO jibber jabber stage bligsem - we are in the front line
have a god jibber jabber time

peter

[Srenner]

I spoke briefly with the brake manufacturer and he was somewhat encouraging. Without any overall impact on pricing, he figures he can do production runs as small as 300 units. Of course, he was not able to do a cost estimate standing in my back alley.

Using the Datsun 240 9" drum as an example, with which he is very familiar, he is reasonably certain any bolt pattern can be had. This might be helpful should separate hub/drum assemblies be required.

Are we still at a stage where wheel strategy and hub/drum choices are not mutually exclusive?

[PJGD]

Incidentally, contrary to Jack's posting of 10th August 2010, I am pretty sure that the Jowett wheel stud PCD will be 7.0" (177.8 mm) and not the 180 mm that his wheel supply house determined the PCD to be.

Just wanted to get that in here before hardware is actually ordered. To check this, I have created a drawing with two circles, each with 5 equally spaced holes; one is the 7.0" PCD and the other is 180 mm PCD. This template can be found here: https://jowettnet/forum/download/file.p ... &mode=view

[Amy]

[quote="PJGD"]Incidentally, contrary to Jack's posting of 10th August 2010, I am pretty sure that the Jowett wheel stud PCD will be 7.0" (177.8 mm) and not the 180 mm that his wheel supply house determined the PCD to be.

Just wanted to get that in here before hardware is actually ordered. To check this, I have created a drawing with two circles, each with 5 equally spaced holes; one is the 7.0" PCD and the other is 180 mm PCD. This template can be found here: https://jowettnet/forum/download/file.p ... &mode=view

[Forumadmin]

Jack and I measured the distance between centres of two studs as 109.4 mm on a Jav hub. Half of that is 54.7mm which becomes the opposite side in a right angled trangle with the hypotenuse as the radius of the hub PCD and the angle as 360/10 degrees. Using to calculate you get radius of 93.1mm or a PCD of 186.2

We have looked on the Jav to see the two major points that limit wheel width and offset. On the front the distance on full lock from the rubber boot covering the upper link to widest part of standard Jav tyre is about 20mm. We will need to measure the distance from this tyre face to the hub face. This distance governs the inside offset. The outside offset is limited by clearance on the rear wheel arch which is about 15mm. The standard Jav tyre inflated width is ???. (Jack will measure and do wheel dimensions as well.)

But I have measured my SAAB wheels fitted with 165SR15 86S tyres. The tyre width is 150mm , the distance from inner bead (outside edge) to hub face is 98mm and from outer bead(outside edge) to hub face is 9mm. This gives an offset from centre line of wheel to hub face of 44.5mm. On the Jup with rubber suspension these needed 10mm of spacers to clear upper link. The rear is not critical on the JUp so I also have spacers on there; but with this offset it is possible not to have spacers on the rear and thus have the wider tyre which will not rub on wheel arch. This is from memory and it is 20 years since they were on the car!

The 16 "wheels currently on the Jup were specially made and I will need measure the spare. These were designed to have a larger offset so that you can adjust rear clearance and front clearance with spacers.

Note that with wider high profile 16" taxi tyres the tyre can rub on the front wheel arch of the Jav on full lock and on full bounce and half lock. This should not be a problem with lower profile or smaller 15" wheels.

[Amy]

I should have some more measurements tomorrow morning at some stage, depending on how long they spend MOTing the Bedford first thing, and if we get to the test station and back without incident
Jack.

No idea whose account/login I am using now! Apologies for the delay, as I had suspected getting to the test station and back didn't go without incident, so the Bedford is now parked up after misfiring, backfiring, cutting out and finally giving up 30 yards from its home, without getting anywhere close to an MOT station.

As below, Keith has calculated the PCD as significantly larger than 180mm, and having eyed it up and done some measuring I am sure it is bigger than that - measuring the PCD is quite difficult, but it just wouldn't fit a 180mm circle wheel, the studs would hit and certainly not be centred in the holes.

The rear tyre has clearance on the Javelin arch approx 25mm - it will hit on the edge of the arch at about 10 o'clock (drivers side) and 2 o'clock (passenger side) so the offset or increased width can't come out far. On the upside a 15" wheel can have as much offset as you like on the front with no clearance problems, the difficulty on the front with a 15" tyre will be the inside measurement.

So in short we need to keep the outside width on the rear almost the same, and the inside width on the front almost the same, resulting in a car with a wider stance at the front than the back - clearly we need to work on this before placing any orders.

Jack.

[Srenner]

Hello All:

My ciphering on the PCD comes up with 7.25". IMHO, it seems more likely to be denominated in Imperial units rather than Metric. This falls about 2mm shy of the KC calculation, still a significant variance.

Perhaps Mr. Dingle can PDF a 7.25" pattern for us to try?

Cheers!
Scott

[Srenner]

Whoops, glasses help when reading the numbers off micrometer! Should be 7.35", which is about 186.7 mm. Let's try that one on the Dingle Device.

[PJGD]

Scott,

I have created two new templates for people to try. My first attempt at posting them to the gallery did not work, but a second attempt using .png graphic files did work.
You can find them here: here

[Srenner]

Phillip:

It occurred to me while I was rowing this morning that Keith's number is correct as it is 7 1/3". I have to say
I thought I measured carefully, but probably missed by a little resulting in my .02 error. It makes sense to me to think Jowett would have used inches, and why not 1/3?

I will use the 7.35 template and I expect it will fit just fine given the inherent margin of error in our methodology.

Scott

[PJGD]

Scott,
I am now better than 99% confident that the Jowett wheel studs are based on a 7.375" PCD. I have just measured a rear hub on my Jupiter using my trusty Starrett dial caliper (which, being made in America, you have to believe!). First I measured the "over the threads" dimension from stud-to-stud going all around the hub thus getting 5 dimensions, then I measured the chord across each alternate stud again getting 5 measurement. I would agree that in a certain sense these are not particularly easy measurements to get accurately, which is why it is necessary to make multiple checks and then average. So, averaging for each, I get: 4.71" stud-to-stud, and 7.38" across the chord.

This works out to a PCD of 7.375" (187.325 mm) as you can see on my latest template here: https://jowettnet/forum/download/file.p ... &mode=view

[Srenner]

Hey Phillip:

Tried to print out the template but could not get it to separate from the surrounding page.

Who knew it would be so hard to get a good measurement? I was using dial calipers, as my micrometers don't go big enough, so my measurements are suspect.

Off to the races this week, so fooling about with the drum will have to wait.
Cheers,
Scott

[John Dolphin]

I can Confirm that the Wheel Stud PCD is 7.375". I have a Jowett drawing of the Jupiter wheel. I'm not sure it will copy too well but I'll try taking a photo and posting it.

[PJGD]

John, yes please post a photo or scan of the Jowett drawing.

I have been working on a drawing of the Jupiter wheel by taking measurements from one of my wheels, but obviously an original drawing will be the oracle!

Philip.