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Discussion Starter #1
seems that Volvo does NOT recommend a 6 mm offset shift.<br>It's bassman from the V50/S40 hangout.<p>The S60R has 46 mm Pegasus wheel. The S60 has some other wheels with 49 mm offset.<p>So either Volvo recommends a 3 mm offset shift for the same suspension (thus changing scrub radius by 3 mm), or else the S60 R suspension's scrub radius and steering geometry are so different that they have a different offset wheel. Indeed, the R uses only Pegasus. The non-R versions use only non-Pegasus. <p>Does anyone have an opinion on whether the 3 mm offset shift in S60 wheel represents a scrub radius shift between S60 and S60R, or a major steering geometry shift?<p>
 

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Re: Wheel offset, scrub radius question (bassman)

As mentioned in previous threads over and over, offset is just a small part of finding out if a wheel fits or not. The shape of the wheel is another important aspect of it. ET49 on the R would kill the lining as that would push the wheel inboard. A few R owners are putting in 5mm spacers (ET41) and even 10mm spacers (ET36) to offset the rubbing the stock Pegs have.<p>Not exactly sure what your question is but if you plan on putting Pegs on your non R, you're fine.
 

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Re: Wheel offset, scrub radius question (bassman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>bassman</b> »</i></TD></TR><TR><TD CLASS="quote">seems that Volvo does NOT recommend a 6 mm offset shift.<br></TD></TR></TABLE><p>Please provide the literature where it says that .<p>Plenty of people are running ET38 wheels and even more people are running 5, 10 and 15mm spacers. <p>So what exactly is your post about???
 

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Re: Wheel offset, scrub radius question (bassman)

Most of the other rims offered by Volvo are 7.5J, the Pegs are 8J wide.<br>Added to that the calipers need clearance and even while already limited in angle the rims need to be mounted without rub. We all know Volvo went to the maximum possible with this setup.<br>Some people reported rub on stock R's.
 

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Re: Wheel offset, scrub radius question (Johann)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Johann</b> »</i></TD></TR><TR><TD CLASS="quote">Some people reported rub on stock R's.</TD></TR></TABLE><p>Most people have rub on stock Rs at full lock.
 

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Re: Wheel offset, scrub radius question ("R" Kelly)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>"R" Kelly</b> »</i></TD></TR><TR><TD CLASS="quote"><p>Most people have rub on stock Rs at full lock. </TD></TR></TABLE><p>I do not agree. Maybe most who have changed tires to the wrong 245 size?
 

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Re: Wheel offset, scrub radius question (Johann)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Johann</b> »</i></TD></TR><TR><TD CLASS="quote">I do not agree. Maybe most who have changed tires to the wrong 245 size?</TD></TR></TABLE><p>Johann, I had rub before I switched... <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/tongue.gif" BORDER="0"> <p>And there are 30 R owners in the local area, most have reported rubbing as well. <p>Also, at least half the board has experienced rub on stock, but I will double check to make sure drugs aren't messing with my memory. <p> <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0">
 

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Re: Wheel offset, scrub radius question (Johann)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Johann</b> »</i></TD></TR><TR><TD CLASS="quote">Most of the other rims offered by Volvo are 7.5J, the Pegs are 8J wide.</TD></TR></TABLE><br>This is the key issue. I guess Volvo needed to push the wider rims a little further outboard to avoid/minimize rubbing and create caliper clearance, hence a small change in offset.<p>You really want to avoid big changes in offset because it changes suspension loads (and feel) during turning and braking. I had a car once with really wide aftermarket wheels. I suspect the scrub radius was ridiculous. Felt like crap during heavy braking (steering wheel "fight").<p>I imagine ABS requires a small scrub radius to avoid excessive load inputs into the suspension when it does it's pulsing thing.
 

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Re: Wheel offset, scrub radius question (Dyno)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Dyno</b> »</i></TD></TR><TR><TD CLASS="quote"><p>You really want to avoid big changes in offset because it changes suspension loads (and feel) during turning and braking. I had a car once with really wide aftermarket wheels. I suspect the scrub radius was ridiculous. Felt like crap during heavy braking (steering wheel "fight").<p></TD></TR></TABLE><p>Thanks. That is the general point of my particular inquiry here. I'll clarify.<p>First, does Dyno or others have an opinion about how many mm specifically is a too large change in scrub radius? I agree with Dyno's general statement: going to a big change in scrub radius is a bad idea. How big of a change is the million dollar question from what I can tell!!!<p>Then, for me to clarify: sorry, I misspoke. I did not mean that Volvo officially documents anything good or bad about 6 mm offset change. Indeed, they don't mention it anywhere. What I've seen on the S40/V50 car is that all wheels are 52.5 mm offset, even the wider 18x7.5 wheels. In fact, they go as far as to add steering stops with the 18x7.5. They could have gone to a lower offset to get better fitment, but instead they kept the same offset to keep the same scrub radius.<p>Then there's S60. My main question of this topic is whether the 46 mm is a offset and scrub radius change compared to the 49 mm normal wheel, or if the R has a suspension so different that 46 is the optimized value for the S60R while 49 is the optimized value for the S60. I agree with the folks who mention that the 8 inch wide wheel needs more clearance, so it might seem that 46 mm is used to help gain clearance. In this case, it's a 3 mm scrub radius change. But the S40/V50 car does not move the offset to gain clearance going to a wider wheel - instead, it uses steering stops!<p>If people are using ET38 wheels, and/or 5, 10, and 15 mm spacers, then it would seem like changing the scrub radius by 10 or more mm is okay. Does anyone have weird steering effects?<p>
 

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Re: Wheel offset, scrub radius question (bassman)

The R also uses different steering stops. <br>The 4 piston calipers used on the R are wider compared to the single piston type calipers used on the other models.<p>Strength of the rim seems to have a part in the ET decision.
 

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Re: Wheel offset, scrub radius question (Johann)

Yeah, but I have to agree with R Kelly, some Rs rub (stock), some just don't.<br>I believe that since no two (Rs) seem to be exactly the same, one may be a mm or two lower, that small amount could cause a rub.<br>Also the steering stops may be adjusted a bit differently on some.<br>These car's clearances seem to be close that if one's just a bit off, it will rub.<br>Take mine, lowered, 18" wheels and tires with only a 5mm spacer and it doesn't rub one bit <IMG NAME="icon" SRC="http://********************/smile/emthup.gif" BORDER="0"> In fact, it never rubbed with 18s and Michelins even before it had spacers. Go figure?
 

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Re: Wheel offset, scrub radius question (Johann)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Johann</b> »</i></TD></TR><TR><TD CLASS="quote">The R also uses different steering stops. <br>The 4 piston calipers used on the R are wider compared to the single piston type calipers used on the other models.<p>Strength of the rim seems to have a part in the ET decision.</TD></TR></TABLE><p>I agree on the stops and the need for clearance to the caliper. But the knuckles, struts and hubs are the same between the R and other S60's, so the basic geometry is the same, no?<p>I think the different offset of the Pegs is in part for strength but mostly to intentionally reduce the already-negative scrub of the chassis design. With the increased torque from the B5254T4, the reduced scrub reduces the torque steer effect, important on the R. Because the tires are wider, their extra squirm would amplify this effect, too. So they change the offset to compensate.<p>The difference is small, but I believe the scrub radius is too. I'm actually surprised folks here using spacers don't notice any changes...<p>Tom.
 

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Re: Wheel offset, scrub radius question (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote">but mostly to intentionally reduce the already-negative scrub of the chassis design. </TD></TR></TABLE><br>So you think the R is closer to zero, but still negative? If so, the guys with wheel spacers are probably just a little bit on the positive side of zero. Maybe not enough to be noticeable.
 

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Re: Wheel offset, scrub radius question (Dyno)

Yep, and yep. I think the spacers swing the car from slight negative (~-10mm) to zero or slight positive. However, a pair of ET38's and a 10mm spacer would drive the contact patches 20mm outward. I would certainly expect to feel that. Maybe nobody is doing that far.<p>Tom.
 

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Re: Wheel offset, scrub radius question (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote">Yep, and yep. I think the spacers swing the car from slight negative (~-10mm) to zero or slight positive. However, a pair of ET38's and a 10mm spacer would drive the contact patches 20mm outward. I would certainly expect to feel that. Maybe nobody is doing that far. Tom.</TD></TR></TABLE><p>I was running 15mm in back for a while. I know at least 5 people on here are running 15s in back. <p>I'll be running ET42 + 10mm very soon (14mm). What exactly do you think that does?
 

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Discussion Starter #16
Re: Wheel offset, scrub radius question ("R" Kelly)

Quicky on scrub radius effects. I'm "studying" it because I'm planning to purchase new wheels for my V50 and this parameter is directly affected by wheel offset, and because I'm a nutty engineer and can't help myself but to try to get the bottom of something.<p>Effects ON steering wheel FROM drive train: torque steer, feeling bumps, feeling braking<p>Effects FROM steering wheel ON drive train: easy or hard steering, degree of linearity of how the steering feels versus speed and how much turn and how close to the limits of the car<p><br>FWD usually have a bit of negative scrub radius to combat torque steer. I'm not so sure 0 scrub is less torque steer. The negative is required to cancel the effect. 0 scrub might be more torque steer than negative. 0 may be less feel of the wheel.<p>So we have three zones: negative, 0, positive<p>negative is what Volvo (probably) designs in to help combat torque steer. Presumably negative, being non-zero, helps give some feel when actively steering.<p>0 may have decent torque steer. 0 is ideal by some folks in theoretical discussions. But 0 might also minimize the feel of the steering ON the drive train. <p>positive has the "bad" steering effects, and lots of feel (good), perhaps too much effort (not good).<p>So folks who go to wider and wider setups get better looks and better handlng due to the widened track. But their steering has to be affected. The big question is how many mm really matter! I have no idea. All I do know is that the suspension design engineers choose stuff based on lots and lots of factors. <p>Tom points out that a small change might move the scrub radius from some negative towards zero. More change is likely to go past zero. Not sure what all that means, and which is better or worse. It would be weird if going to zero were bad, but going FURTHER to positive were actually good. But it might be the case?<p><br>
 

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Re: Wheel offset, scrub radius question (bassman)

So, no effects on the rear wheels? <p>As far as the front wheels, I didn't notice anything different when I ran 15 or 10mm spacers up front. Currently run 10mm, both on autobahn and Nurburgring...<p><IMG SRC="http://smileys.smileycentral.com/cat/36/36_5_11.gif" BORDER="0">
 

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Discussion Starter #18
Re: Wheel offset, scrub radius question ("R" Kelly)

Good question on rear. I have no idea! Mostly I've been thinking about effects of the front wheel offset changes on steering feel. The rear may have effects also that completely beyond me.<p><br>Thanks for your observation. Sounds like 10, even 15 mm shouldn't be too much of a problem for the steering feel for most folks. I'm not sure if I should be surprised that 10 to 15 mm are very similar to original in steering feel, if it should seem obvious since it is "JUST" one little centimeter!<p>I think other posts (Subaru WRX STI) have mentioned that folks do feel a steering difference at, for example, 10 mm. <p>
 

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Re: Wheel offset, scrub radius question (bassman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>bassman</b> »</i></TD></TR><TR><TD CLASS="quote">FWD usually have a bit of negative scrub radius to combat torque steer.</TD></TR></TABLE><p>Definitely negative scrub on the S40/V50 - Volvo docs say so. Somewhat less clear on S60 but most all FWD's have negative scrub, one because they can and two because FWD torque steers otherwise.<p>Spacers on the rear won't change much but increase strain on the wheel bearing slightly. There aren't any steering effects to speak of there.<p>RKelly - 14mm increase will probably have minimal to moderate change in "feel", increasing feedback of bumps and braking. Will probably increase torque steer some, but AWD will counteract that. It might be noticeable, might not. If you upsize your tires the effect might be greater due to increased squirm under torque. Mostly speculation however, since so many variables are in play here.<p>Tom.
 

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Re: Wheel offset, scrub radius question (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote">RKelly - 14mm increase will probably have minimal to moderate change in "feel", increasing feedback of bumps and braking. Will probably increase torque steer some, but AWD will counteract that. Tom.</TD></TR></TABLE><p>Hey, thanks for tips. <IMG SRC="http://smileys.smileycentral.com/cat/36/36_1_11.gif" BORDER="0"><p>Right now I have 10mm spacers up front. <br>Soon I will have ET42 Rims plus 5mm spacers up front (9mm spacer)<p>5-10mm spacer front, 10-15mm spacer rear is what I always reccomend. <p><IMG SRC="http://smileys.smileycentral.com/cat/36/36_1_53.gif" BORDER="0">
 
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