Have you actually measured for maximum wheel offset ? 38mm+

Discussion in 'SRT Hellcat General Discussions' started by dhg66, Feb 7, 2016.

  1. dhg66

    dhg66 Hellcat Member

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    i installed the b woody shorter rear end links today and crawled under the car to measure for wider tires and wheels and am wondering how many people actually measure to determine the maximum possible positive offset and where the 27.4 mm number came from,. i measured for clearance and i have over 1.75 inches of inside clearance with the stock wheels and tires ... if i had a better go no go gauge it might be closer to 1.85" so subtract .2 inches for comfort clearance and there is 1.55 inches to go inside ... the 315 nitto motiva is 40.6 mm wider that the stock zero so on the stock wheel the tire takes up 20.3 mm of the 1.55 inches (39.37mm ) leaving 19 mm to move the wheel in Adding the 19 mm to the 18.4 mm stock [positive offset gives 37.4 mm positive offset possible with the nitto 315, with these measurements it means that nitto will only stick out 1 mm over stock. ... has anyone measured and got different or the same numbers as these. would like to hear from people that have actually measured and not secondary word of mouth. i want to order my wheels Tuesday and want to be sure that what i get fits without sticking the tire out too much

    thanks in advance
     
  2. dhg66

    dhg66 Hellcat Member

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    i got the clearance wrong, it is more like 1.25 inches so please disregard my bad calculations.
     
  3. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    These are my first person calculations for you quickly during my first cup this morning. Given the following:

    1.Stock wheels are 9.5" wide/19 mm backset

    2. You shall not mount 315/35 on a 9.5" wheel

    3. You can install on a 10.5" wheel on the rear of your car and further, you would like the exterior edge of that wider wheel sitting nearly where the stock wheel sits.

    New 10.5" - stock 9.5" width = 1 inch wider. divide by 2 = 1/2" each side
    Add 1/4" of backset (move the wheel closer in) 1/4"=6.35mm
    19+6.35=25.35 mm revised backset, puts a 10.5" wheel just 1/4" further outside than the stockers. I have seen 10" and 10.5" backsets from 20-27mm. Don't get 35mm, or you won't be able to even bolt them up. You were dreaming that number or had it twisted with another number, but it was not wheel backset for a Challenger.

    That is the position of the wheels. Now just as important here because the tires will rub before the wheel is a quick study of some popular tires.

    Stock; 275/40/20 Pirelli PZero section width is 10.9". A Motivo is 12.52" ( be careful), a NT05 is 12.4". A Pirelli PZero 315/35 is 12.6" wide. I will give you this info. A 12.6" wide tire rubs at a 20mm backset (10.5" wheel). A 12.4" wide tire DOES NOT rub at a 27 mm backset. When using the tires with these measurements, there is not much clearance between the tire and inner wheel well, be careful, there is not 1.25" clearance with the new tires in play.

    My advice study all of our wheel and tire threads because lots of people have tons of info and pictures on wheels, tires, brands sizes backsets, sticking, holding and riding qualities.
     
  4. dhg66

    dhg66 Hellcat Member

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    thank you for the insight. as I mentioned I messed up on the original measurements ... did not measure near the very front of the tire where the clearance is the least. This is now where a 1.3 inch go no go gauge just makes it between the tire and the inner fender bulge (bump).

    The only thing I don't agree with is how a 12.6" tire rubs at 20 mm offset and a 12.4" tire does not rub with 27 mm offset ... the inside difference between the tire width is 0.1 inches or 2.54 mm so you should have the same tire clearance with a 12.6 inch tire with 24.46 mm offset as with a 12.4 inch tire with a 27 mm offset, unless the 12.4inch tire is also shorter that would make a difference ... our your experience with those exact tires based on actual installs ? I think I will be a little more conservative and give it another 1/8 inch clearance. any other input is much appreciated. Thank you
     
  5. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    You can disagree if you want, you are the OP. Facts are facts, a 12.6" section width Pirelli PZero 315/35 10.5" wheel w/20 mm backset rubs. I owned them, now they are trash. I have 25 mm 10.5" custom wheels. They were installed with a 5 mm spacer = 3/16"= 20 mm backset.

    Facts are facts, members with 25-27 mm backset with 10.5" wheels Nitto NT05 315/35 don't rub. Same wheel type and manufacturer, FYI.

    FYI the difference btw a PZero and a NT05 315/35 is more like one quarter inch, period, put your ruler down. Also a I believe the fundamental design of the shoulder is different (I.E. The Pirelli seems more square).

    You keep measuring, and hope you are correct. Good luck, it is your thread, we here at the Forum with lots of input and conversations try to help. You apparently have not viewed tons and tons of other threads on this same exact thing, I was attempting to make your day easy before you order tomorrow.

    Oh, I just read your OP again, if you are going to put a 315/35 on a 9.5" rim, disregard everything, I have helped you with.

    If you like the Motivo's, study this thread: Bigger Wheels
     
  6. dhg66

    dhg66 Hellcat Member

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    thank you very much for the link to this post, I had searched MOtivo and nothing came up, maybe I spelled it wrong.

    Below is extracted from the original post, so with 21 mm offset he had 3/8 to 1/2 inch clearance though it looks closer to the push pin than that in the pic that is posted . I think I will go 25.4 mm (1 inch) positive offset, if they touch, I'll use those rims for the narrower NItto DR and then order another set of wheels with a little less offset.

    "OK, Heres the deal. Bravado Tribute's 20x11 21mm offset with 315x35 Nitto Motivo's fit with no problems. All I had to do was remove one of the inner fender mounting push pins, push the inner fender towards the rear of the car, drill a new hole and reinsert the mounting pin. I started to use the heat gun then tried this, I actually have over 2" clearance between the rear of the tire and the inner fender. Upper shock is about 1" from tire. Front clearance from inner fender to tire is about 3/8" to 1/2" close but will not rub I could have heated and push in some but if it doesn't rub why bother. I would have loved to have had 12 to 14mm more offset to get them under the fender better, but then I would have to do a little work on the front inner fender. Now I need to get billet Tech to make me some center caps 68mm diameter. Not sure why some pics are rotated.? "
     
  7. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    Good luck. My expensive wheels are cut at 25 mm. Yep, use them for drag racing or use a small spacer when all goes wrong. Exciting times, post up your pictures when you are done.
     
  8. dhg66

    dhg66 Hellcat Member

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    did you measure the P zero 315s to confirm that they are in fact 12.6 ? I am wondering if some of the tires do not measure out to the stated width specs, some narrower some wider, maybe

    With your wheels cut at 25 mm, which brand and size of DR do you use and do you also use the spacer with the DR ? I want to be sure that my back up plan when cutting to 25.4 mm to use a DR without a spacer will work.

    I have also heard that many of these wheel manufacturers can only make wheels in 1/8 inch increments in offset

    Thank you
     
  9. dhg66

    dhg66 Hellcat Member

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    what brand wheels did you go with ? I am planning to go with MHT who make Foose.
     
  10. dhg66

    dhg66 Hellcat Member

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    a little more of your time would be much appreciated.
    i have a high dollar 24 inch dial caliper so i measured the overall width of the factory p zeros mounted on the factory rims, they are exactly 10.8 inches wide. i have the Motivos not mounted and they measure 12.95 inches wide ... so i measured the inner mounting area of the tire and got 11.72 inches, so a 10.5 inch rim or 11 inch rim would suck the tire in a bit but .22 inches per side in order to get to the 12,52 spec seems like a lot so i think you are right that 1 inch offset would rub, just not sure how the guy with the 11 inch bravado wheels has clearance, after all this i am still not sure what offset to use.
     
  11. DGatzby

    DGatzby Gold Member Hellcat Car Club HCC Charter Member Midwest Regional Pres.

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    I have Triumph Performance Wheel mono blocks. They are cut to exactly 25 mm backset. I do not change out drag radials on them. They have my show/street tire. At this point I am waiting for Triumph to answer a litte question and we shall know if we are going with NT05's or buy two 305/35 PZero's for the rear. I think tire manufacturers are accurate in their specs the problem is that people mount tires on in appropriately narrow wheels or do not understand what specs are given for what. Besides wasting money it is not safe. We knew we were on the edge last year. I also road race the car (not these wheels/tires) and may have pushed a few turns with these on to get them to rub, when others may not. I don't care. Do what you want, they won't work at that spec.
     
  12. dhg66

    dhg66 Hellcat Member

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    i looked at the bravado motivo thread again and looked at the pics and there is little clearance at the front of the tire but it clears, and i would not want to get any tighter than that so this is known to work with 21 mm offset so that is what i am going to go with, 21mm and hope the manufacturer has proper tolerances, thank you for all the help and preventing me from making an expensive mistake.
     
  13. TrackDay

    TrackDay Silver Member

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    When you are bouncing back and forth between different wheel widths maybe it would be easier to talk in terms of back spacing. Offset has to include the width of the wheel. If all you care about is the inboard clearance there is only 1 max back spacing answer.
     
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  14. dhg66

    dhg66 Hellcat Member

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    yes thank you backspacing would make it a lot easier, i think i am settled on the 11 inch wide bravado example with 21 mm offset, from the pics he posted that is about as close as i want the tire to get in the front i appreciate all the help
     
  15. boosted srt

    boosted srt SRT Hellcat Supporter Gold Supporting Member

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    Bismark is the man,

    When you make a purchase from a premium supplier like Triumph Wheels not only do you get a wheel that can withstand nearly all performance requirements that
    your car has available, also looks to match and customer service that cannot simply be matched.
    Try and call Bravado or the other Mfgr's like TSW and Movado the list goes on all you get is some phone sales dude who has no idea, nice but not at all equal.
    I called TSW they wanted me to except the idea that the bolt circle on their Nurbergering was close but not exact 5x114.3 vs hellcat 5x115 i guess stress the studs
    it SHOULD be ok.
    Its like comparing a Bald Eagle to a Buzzard.

    My wheels will be here Thursday went with mx4 w/ 27mm offset 10.5"x20 gonna go with 315 Nt05r.
    You wont regret his knowlege of wheels, probably wont be matched.

    Just my opinion
    Triumph
     
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