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Cromodora CD26 5J 13 foul large struts?


Oldtimerfahrer
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Hi all!

I searched but I did not find an answer here where there is an answer to so many things....so I'm hoping the question isn't too daft. I have a nice set of Cromodora rims that I wanted to mount a set of XAS tires on. They are 5inch, not the 5.5 inch ones that Anders posted in the Wheel database but the same design. I had them painted, I have the original caps, but now on trying to mount them, no joy.

 

Now the question...When I mount them on my ti, which has the large struts like the tii, the inside of the rim fouls the top of the brake caliper. It actually is in contact with top bolt that holds the caliper together. Its a recessed allen key style bolt, so its not sticking out unduly. I mounted the wheel with tire and it acts like a lathe, cutting quite a bit off the inside of the rim at a point where the shoulder of the rim. It actually continued to remove material and the lug nuts became loose, which means that if I tightened them, it would continue to remove material. I had not read anywhere that there was an issue with these rims, my cosmic rims are tight as well so you can't place balancing weights anywhere you like.  You can see on the second picture the area where the paint and material have been removed.

 

Reason I wanted them in the first place was that the small XAS' looks kind of strange on a 5.5 inch rim (flank of tire is essentially narrower than the rim). Has anyone had this problem? I am kind of hesitant to bring them to a machine shop and create a set of "front rims" by removing materials because if I make toast out of them then its a total loss. There seems to be a shoulder there but I don't see a practical way of measuring how much material is available to remove. I guess not many people are driving them any more, but would be a shame to ruin them. Any suggestions?

 

Andrew

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Andrew,

 

Just so you're aware -- and you may already be -- the Cromodora CD26 was reportedly a 4x98 PCD rim, manufactured for the Simca 1200 Coupe

 

http://www.histowheels.com/Cromodora/

 

I realize there might be errors or omissions on the History of Wheels site, and I have nothing but respect for Anders, who posted 5.5x13 CD26’s on our Wheels Database.  But, otherwise, I only find CD26’s referred to as 5x13 rims with a 4x98 PCD and excellent for Fiats.

 

Fiat Vignale Samantha '69

 

So you're possibly combatting two issues: incorrect PCD, incorrect ET.  Theoretically, there could also be a third issue: the thickness of the casting.  But in most cases such as this, modifying the ET, by adding spacers, may solve the clearance issue.

 

I have had 4x98 PCD Campagnolos (magnesium alloy, like your Cromodoras) re-drilled to a 4x100 PCD, as I've described in earlier threads regarding my surprise at finding the same Campy casting in both 4x98 and 4x100 PCD's. There is generally a steel insert at the lug holes on these magnesium alloy rims and re-drilling consisted of pressing out the old steel inserts, pressing in new blank inserts, and drilling the new inserts for a 4x100 PCD.  The sensitive issue is that when many rim repair shops hear you have magnesium alloy rims, they freeze up, fearing the highly flammable -- sometimes almost explosive -- magnesium rims of the 1950's.  My re-drilling went without a hitch, and was performed by a shop that fully understood they were magnesium alloy, but which no longer works on rims not sold by themselves.

 

I don't see a published ET, but the lack of any "dish" to the face suggests to me that the C26 could be, for instance, an ET35 rim.  Carefully measure a couple of your rims to determine the ET.  Then get spacers equal to the CD26's ET less ET27 -- a sweet spot for an '02.  But beware, you may need to install longer wheel studs along with your spacers.

 

Beautiful rims, by the way.

 

Regards,

 

Steve

 

 

 

 

Edited by Conserv
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Hi Steve!

A real shocker, thanks for the insight. I would have thought I would have noticed if the center dimension was different...but perhaps someone has already replaced the inserts as the wheels sat perfectly on the studs and I tightened by hand and the rears went on normally. I will measure them carefully, I think the offset is published in the German TUV wheel catalog, but I will make double sure. The wheels are pretty, especially without the caps. The caps date them severely and mine have very yellowed plexiglas covers hiding the old black and white BMW roundel emblems. So it makes the whole thing a bit antiquated looking.

Thanks!

Andrew

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9 hours ago, Oldtimerfahrer said:

Hi Steve!

A real shocker, thanks for the insight. I would have thought I would have noticed if the center dimension was different...but perhaps someone has already replaced the inserts as the wheels sat perfectly on the studs and I tightened by hand and the rears went on normally. I will measure them carefully, I think the offset is published in the German TUV wheel catalog, but I will make double sure. The wheels are pretty, especially without the caps. The caps date them severely and mine have very yellowed plexiglas covers hiding the old black and white BMW roundel emblems. So it makes the whole thing a bit antiquated looking.

Thanks!

Andrew

 

Andrew,

 

Do your rims have “CD26” cast into them?  With Cromodora, the model designation generally indicates both a rim size and a PCD.  But, as I mentioned regarding my own surprise at finding two 4x98’s among my 4x100’s Campys, Campagnolo — the “other” high-quality magnesium alloy Italian — produced certain rims, with model number “40714 BP” cast into them (first photo) and then drilled some as 4x98 and some as 4x100.  The 4x98 versions received a sticker saying they were, in fact, model 40571 BP (second photo), while the 4x100 versions received a sticker confirming they were, indeed, model 40714 BP.  Maybe Cromodora was taking a similar approach.  But, at least with Campagnolo, there was plenty of documentation of the two distinct models.

 

When comparing 4x98 and 4x100 PCD’s, since the diameter of the bolt circle is only 2mm less, it means each bolt hole is 1mm closer to the center hub, a subtle difference.  A 4x98 rim will always slip easily onto 4x100 studs.  But the studs will not be centered within the bolt holes and tightening the lug nuts puts uneven pressure on the rim, creating stress where it was not anticipated, especially a bad thing on an antique rim, and perhaps a worse thing on magnesium alloy, which is more brittle and prone to natural deterioration than aluminum alloys.

 

That said, lots of BMW and Fiat owners unwittingly use rims with the wrong PCD.  Others knowingly use rims with the wrong PCD, some using “wobble nuts” a lug nut designed to mitigate the PCD mis-match.  Needless to say, rim manufacturers do not endorse wobble nuts; they only endorse correct PCD rims.

 

My PCD measuring tool, less than $10 on eBay, can generally detect the difference between 4x98 and 4x100 PCD’s.  If I had your rims, I’d measure them and, honestly, evaluate that measurement — I originally tried to deny my two 4x98 Campys were 4x98.  I shuffled the rims several times and re-measured all six rims, each time finding two that appeared to be 4x98.  They were.

 

But the offset of your rims also seems to suggest a rim not designed for an ‘02.  A model designed for an ‘02 should not need spacers — not that there is a particular issue with the use of small spacers.

 

My recommendation?  Make certain your rims have the correct 4x100 PCD, whether that is (a.) as they came from the factory, or (b.) as previously modified, or (c.) as modified now.  Then use spacers to make up the difference between the rims’ offset and a more optimal ‘02 offset.

 

The rims are, indeed, some of the highest quality and best looking rims of the period.

 

Best regards,

 

Steve

 

 

 

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Edited by Conserv
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Hi Steve!

Thanks, I finally got home and went to the basement to look at the insides of my rims. The CD is cast in the rim, the 26 is stamped. There is a 1 stamped in one of the webs and the 3rd think looks like a date of manufacture 71 is at the top in any case with 12 boxes below. I took a picture of the cap as well, seems they have been mounted on a BMW for quite a while judging from the emblem and its aging. Previous owner of the rims had never mounted them.

I measured, albeit not very scientifically by putting a conical drill bit in two lugs and it seems to measure 100. The inserts do not appear to be offset but as you said, with the naked eye the 2mm on each side are minimal. Do you know what the correct method to measure is? I suppose best would be a stud that is not installed and then a vernier to get the centers...

I have a few months of time as my car is on loan to a museum until April (free heated winter storage) so I can measure the offset of the rims and get the right spacers.

I looked in the German TUV wheel catalog, there are no Cromodoras listed in 5j x 13, only 5.5 and those are the CD32 and CD96 with 18.5 and 18 offset. Only the CD32 is period correct, starting date 1971, the CD96 is from 1978. Hmm, the disappointment is great, but I suppose I can have a good machine shop measure/replace the inserts.

Regards,

Andrew

 

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Andrew,

 

Here's a PCD measuring tool.

 

https://www.ebay.com/itm/Precise-Tire-Bolts-Wheel-Rims-Ruler-Pattern-Gauge-PCD-Measuring-Tool-4-5-6-8-Lug/191877122944?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

 

I have one and it's not exactly a precision instrument, but it can generally distinguish a 4x98 from a 4x100 PCD. Seriously, the re-drilling of my Campys was no big deal, the shop charged me $50 each.

 

Yes, I can't quite make out the number of boxes with nubs in them (I see nubs in at least 5 of the 12 month boxes) but the rims were certainly cast in 1971.  Those kerfed letters on the "BMW" emblems are much earlier than 1971, probably a 1940's or '50's design.  I would guess that someone found BMW roundels of a suitable size for the chrome hub caps and was either indifferent to or didn’t notice the old-fashioned lettering.

 

Regards,

 

Steve

 

Edited by Conserv
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  • 5 months later...

Hi,

Well, just for posterity, thanks Steve and the previous participants. I decided not to machine the rims, did not find anyone that wanted to modify them anyway. I have now wobbly nuts and 3mm spacers to ensure that the rims don't foul the calipers.

I measured the CD 26 rims and they are

160mm wide

105mm from mounting surface to inner side of rim

25mm seems to be the ET (offset) by my calculation

The spacers would then increase the offset to 28mm. I think Steve said the sweet spot was at 27mm.

I could find no published figures for the ET of these rims but I think my measurements are pretty accurate.

All in all a rather expensivemistake, the wobble nuts are around $5 a piece, the spacers were about $80 for four... ouch. Now I can (still) sell them to a Simca owner...some day. I think they will work well with the XAS tires, which look a bit small on 5,5 in Cosmic rims.

A friend is 3D printing some nice center caps so I will be able to post the result soon...

 

I did score a set of Mahle 6x13 rims and a set of BBS 6x14 basketweaves with caps as a package deal. The basketweaves will go on an E30 that I am hoping to pick up on Saturday. Now I have whole collection of rims, just need more cars to mount them on.

 

Andrew

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8 hours ago, Oldtimerfahrer said:

25mm seems to be the ET (offset) by my calculation

The spacers would then increase the offset to 28mm. I think Steve said the sweet spot was at 27mm.

No - Actually they decrease the offset to 22. That's fine since the wheels are so narrow. Increased scrub radius (caused by ET) does cause increased steering effort and how much you feel potholes and such pits in the road. That said it's probably still just fine for you with the tire size you have but if you feel that kind of drawbacks it's the offset causing them.

 

EDIT. One thing more. I'm not sure about "wobbly nuts" with the not hub-centric wheels/hubs. If there is vibration, that will be caused by the bolt pattern issue and I think the option to get in touch with the Simca owner is the solution. 

 

  Tommy

Edited by Tommy
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Hi,

Yes, the spacers are necessary to clear the front calipers, not to widen the track. I don't need them in the back but the handling might be funky with a different offset front to  back. 

 

I just got my car back last Friday from winter storage, so I will check how snug a fit the spacers are and then drive it. I actually bought the rims from a BMW owner, who had bought them god knows where (but also from a BMW owner) and had never used them. They are quite well travelled rims having changed hands a few times and moved between several European countries, though they have seen no use in at least 10 years. From the hubcaps one would think that they were mounted on a BMW at some point in time, because its a lot of trouble to make up the cap centers. The Plastic centers are a bit finicky to assemble, the yellowing transparent covers are quite old. Wish I new a Simca 1200s coupe owner, I like those... very similar in proportions to the Glas coupe.

 

Thanks again,

Andrew

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