Hi guys here are some modified Penta's and Bundt's enjoy http://www.m-100.cc/forum/topic.asp?TOPIC_ID=6835 
Wide Penta's
- Thread starter motec 6.9
- Start date
SEL_69L
Aristocrat
I am very reticent to fit tyres wider than the standard width of 215mm.
If the suspension allows the car to sink, there is a greater possibility of that the mudguards will crunch into a tyre of greater width than 215mm. I always park with the wheels in the straight ahead position for this reason.
Same applies for tyres of greater outside diameter than standard.
Perhaps it is possible to take the tyre width out to 225mm, but it is essential to consider the amount of offset of the wheel rim so as to retain the zero offset of the steering. If this is not considered, poor handling could result, with a bias of the load taken on one side of the tyre. Shortened life in the suspension bushings would also result.
If the suspension allows the car to sink, there is a greater possibility of that the mudguards will crunch into a tyre of greater width than 215mm. I always park with the wheels in the straight ahead position for this reason.
Same applies for tyres of greater outside diameter than standard.
Perhaps it is possible to take the tyre width out to 225mm, but it is essential to consider the amount of offset of the wheel rim so as to retain the zero offset of the steering. If this is not considered, poor handling could result, with a bias of the load taken on one side of the tyre. Shortened life in the suspension bushings would also result.
BenzBoy
Grand Master
How wide do you go before you start to loose longitudinal contact with the road? I know there is a formula but I don't remember it... (again the memory has reached overload!).
Regards,
Brian
Regards,
Brian
With an wheel offset of e11 and a width of 8" , you can get 255s under the rear of a W116 without rubbing, or fouling.... Maybe wider, but it would depend on the brand of tyre and the design of the sidewalls. If you had the front wheels turned on a 6.9 and the suspension leaked down (or collapsed), I think even the standard wheels and tyres would contact the guards.... I probably wouldn't go any wider than 235s on the front, but I'm not sure they'd be suitable for the standard (6.5") Bundts, or whether they'd rub, or foul. I'll have to check....
It'd be interesting to know how they make the wheels posted by Motec and what MBs they'd suit...
Maybe wider, but it would depend on the brand of tyre and the design of the sidewalls. If you had the front wheels turned on a 6.9 and the suspension leaked down (or collapsed), I think even the standard wheels and tyres would contact the guards.... I probably wouldn't go any wider than 235s on the front, but I'm not sure they'd be suitable for the standard (6.5") Bundts, or whether they'd rub, or foul. I'll have to check....It'd be interesting to know how they make the wheels posted by Motec and what MBs they'd suit...
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SEL_69L
Aristocrat
BenzBoy: It does not matter how wide a tyre / rim combination is, so long the offset for the rim is OK. For zero offset steering (whch the W116 has,) the centre of the contact patch of the tyre on the road must pass through the axis of the king pin or what serves as that axis.
Tyre width and rubbing against the mudguard is a separate issue. Even with standard 215mm wide tyres, with the steering turned hard right or left, the mudguard WILL make contact with the tyre on a 6.9, if the suspension is down.
Wider tyres just exacerbate the problem.
That is why I always leave the steering in the straight ahead position when parked.
Wider tyres at the rear present less of a problem, because the rear wheels do not steer. I have driven a 6.9 with 245's on the rear, and the rear of the car is less likely to break away, when turning under acceleration. I still think the offset for the rear wheels has to be correct so that the life of suspension bushings is not shortened.
Tyre width and rubbing against the mudguard is a separate issue. Even with standard 215mm wide tyres, with the steering turned hard right or left, the mudguard WILL make contact with the tyre on a 6.9, if the suspension is down.
Wider tyres just exacerbate the problem.
That is why I always leave the steering in the straight ahead position when parked.
Wider tyres at the rear present less of a problem, because the rear wheels do not steer. I have driven a 6.9 with 245's on the rear, and the rear of the car is less likely to break away, when turning under acceleration. I still think the offset for the rear wheels has to be correct so that the life of suspension bushings is not shortened.
BenzBoy
Grand Master
"BenzBoy: It does not matter how wide a tyre / rim combination is, so long the offset for the rim is OK. For zero offset steering (whch the W116 has,) the centre of the contact patch of the tyre on the road must pass through the axis of the king pin or what serves as that axis."
Right - I see.
OK try this then:
I am advised of the following - If you're interested simply in the area of contact for tyres I believe the calculation is straightforward and easily derived on the back of an envelope.
If w = gross weight of vehicle in pounds
p = tyre pressure in PSI
n = Number of tyres
c = contact area per tyre (in square inches)
then c = w/np
If the front and rear tyres run different pressures the above formula could get complicated but I haven't derived it yet so I can't say for sure.
Even further - http://en.wikipedia.org/wiki/Slip_angle and http://www.performancesimulations.com/fact-or-fiction-tires-1.htm
Nothing is as simple as it first seems.
Regards,
Brian
Right - I see.
OK try this then:
I am advised of the following - If you're interested simply in the area of contact for tyres I believe the calculation is straightforward and easily derived on the back of an envelope.
If w = gross weight of vehicle in pounds
p = tyre pressure in PSI
n = Number of tyres
c = contact area per tyre (in square inches)
then c = w/np
If the front and rear tyres run different pressures the above formula could get complicated but I haven't derived it yet so I can't say for sure.
Even further - http://en.wikipedia.org/wiki/Slip_angle and http://www.performancesimulations.com/fact-or-fiction-tires-1.htm
Nothing is as simple as it first seems.
Regards,
Brian
I'd be interested to know the limits of wheel offset on a W116. My Centras and Ronals have an offset of e11. The original Bundts are e30. Does anyone know of other wheels with larger (or smaller), offsets that will fit without spacers? From what I've seen later wheels all have offsets well above 30...
On the subject of tyres, I'm still stumped. Wider rubber suggests better grip with a larger contact patch on the road surface. However the larger the contact area, the more the weight of the vehicle is distributed. Think about a bed of nails vs lying down on just one nail. So considering the weight of a W116 (and W107), is there a formula to determine the optimum tyre width? Or should Benzboy's formula be used to determine the contact area and then use a simple LxW to roughly work out the optimum size? I'd imagine any contact patch would be eliptical on both the leading and trailing edges and the shape would vary depending on pressure...
BTW it's less likely rear tyres will contact the body, as the suspension design means they travel in an arc on bump and rebound. Bump introduces negative camber, so the top of the tyres move inwards at the top, thereby increasing clearance at the top (but also reducing it on the inside). To be honest it's a less than ideal design that I think was pretty much copied by Holden and introduced with IRS on some VR Commodores. I've heard they were really bad for premature wear on the inner shoulders and this problem continued until the VT Series II....
On the subject of tyres, I'm still stumped. Wider rubber suggests better grip with a larger contact patch on the road surface. However the larger the contact area, the more the weight of the vehicle is distributed. Think about a bed of nails vs lying down on just one nail. So considering the weight of a W116 (and W107), is there a formula to determine the optimum tyre width? Or should Benzboy's formula be used to determine the contact area and then use a simple LxW to roughly work out the optimum size? I'd imagine any contact patch would be eliptical on both the leading and trailing edges and the shape would vary depending on pressure...
BTW it's less likely rear tyres will contact the body, as the suspension design means they travel in an arc on bump and rebound. Bump introduces negative camber, so the top of the tyres move inwards at the top, thereby increasing clearance at the top (but also reducing it on the inside). To be honest it's a less than ideal design that I think was pretty much copied by Holden and introduced with IRS on some VR Commodores. I've heard they were really bad for premature wear on the inner shoulders and this problem continued until the VT Series II....
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I've just borrowed some late-ish wheels from a seller on E-bay. From what I've seen so far, an offset of e30 is the maximum limit that will fit the rear of a 6.9, on a wheel that's 9.5" wide. A 295mm tyre on 9.5 x 18" e33 wheels will rub on the lower section of the inner guard. Interestingly the original Bundts had what appears to be the maximum offset (e30).
My Ronals and Centras have offsets of e11 and they fit quite well. So really, the wider the wheel that you want to fit, the lower the offset should be. In fact, I'd suggest a negative offset (deep dish) wheel would look the best, but I'd be a bit worried about the affect on handling. From what I've seen, deep dish wheels are quite popular in Europe, judging by some pictures of W116s and W123s. We haven't heard of any adverse handling issues from them....
I'd like to have a definitive answer on this to help members correctly select different wheels. I intend to do some measuring with the wheels off Red Bull and see what's revealed. At this point the limit is e30 - e11 (or less).
The biggest problem we all face is the fact that late wheels have very high positive offsets (e30 and above). In fact I noticed the 21" wheels from an ML have an offset of e60! So the only way to fit late wheels is with spacers that increase the distance between the back of the wheel/tyre and the inner guards. I do like the design of the spacers Styria had made, but I'd be concerned about handling and legality / insurance issues in Victoria.
The other (very expensive) solution is to have some wheels made with a negative offset like the ones shown here by Motec....
My Ronals and Centras have offsets of e11 and they fit quite well. So really, the wider the wheel that you want to fit, the lower the offset should be. In fact, I'd suggest a negative offset (deep dish) wheel would look the best, but I'd be a bit worried about the affect on handling. From what I've seen, deep dish wheels are quite popular in Europe, judging by some pictures of W116s and W123s. We haven't heard of any adverse handling issues from them....
I'd like to have a definitive answer on this to help members correctly select different wheels. I intend to do some measuring with the wheels off Red Bull and see what's revealed. At this point the limit is e30 - e11 (or less).
The biggest problem we all face is the fact that late wheels have very high positive offsets (e30 and above). In fact I noticed the 21" wheels from an ML have an offset of e60! So the only way to fit late wheels is with spacers that increase the distance between the back of the wheel/tyre and the inner guards. I do like the design of the spacers Styria had made, but I'd be concerned about handling and legality / insurance issues in Victoria.
The other (very expensive) solution is to have some wheels made with a negative offset like the ones shown here by Motec....
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These are 9" wide Rials with an offset of e11 (apparently):
http://www.germancarforum.com/older...erved-decay-w116-280-se-fair-weather-car.html
http://www.germancarforum.com/older...erved-decay-w116-280-se-fair-weather-car.html
Over the last few days I've been toying with different wheels to see what fits and what looks the best. And one thing struck me that I bet many prople haven't considered; tyre sidewall flex!!!! Yes it may be that your chosen wheel / tyre combination will fit from a static point-of-view but out on the road, things could be quite different. I'm sure many of you have seen footage of a car during high-speed cornering and seen the substantial flex in the tyres under load.... So having tyres that JUST clear the guards might look good when the car's stationary, but during cornering the tyre's likely to rub on the something and quite possibly let go at the worst possible moment. And we've all seen what can happen if a tyre blows at the wrong time....
http://www.topklasse.org/forums/showthread.php?t=3114&highlight=crash
The biggest problem is that sidewall flex depends on many variable factors and it's therefore not easy to determine how much should be allowed. I'd imagine flex on the front tyres would be far greater than that of the rear.
I've heard it said more than once that with the zero offset suspension geometry of the W116 that wheel offset shouldn't be altered and that handling could be drastically affected. That means anything other than e30 (Bundts) and there could be a problem... I'll have to check whether the steel wheels are also e30. However the Centras and Ronals (Pentas) are e11 (as fitted by AMG) and they are supposed to handle better!!! So is this likely to be a myth?
I know for a fact that 8 x 16" wheels with an offset of e36 will definitely not fit the front of a 6.9. So at the moment the limit is e30 to e11. It may be very difficult to test the lower limit (less than e11 and into negative offsets) as these wheel designs are simply not available here....
http://www.topklasse.org/forums/showthread.php?t=3114&highlight=crash
The biggest problem is that sidewall flex depends on many variable factors and it's therefore not easy to determine how much should be allowed. I'd imagine flex on the front tyres would be far greater than that of the rear.
I've heard it said more than once that with the zero offset suspension geometry of the W116 that wheel offset shouldn't be altered and that handling could be drastically affected. That means anything other than e30 (Bundts) and there could be a problem... I'll have to check whether the steel wheels are also e30. However the Centras and Ronals (Pentas) are e11 (as fitted by AMG) and they are supposed to handle better!!! So is this likely to be a myth?
I know for a fact that 8 x 16" wheels with an offset of e36 will definitely not fit the front of a 6.9. So at the moment the limit is e30 to e11. It may be very difficult to test the lower limit (less than e11 and into negative offsets) as these wheel designs are simply not available here....
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It seems the early wheels were stamped with an 'e' which referred to the offset. I wondered what it was an abbreviation for, so I went searching. Later wheels are stamped 'et' and I found the following for those that like a bit of trivia:
Wheels are usually stamped with their offset using the German prefix "ET", meaning "Einpresstiefe" or, literally, "press depth".
So now you know!!
Wheels are usually stamped with their offset using the German prefix "ET", meaning "Einpresstiefe" or, literally, "press depth".
So now you know!!
I was watching this video and it seems that most of the sidewall flex is near the road surface and therefore it shouldn't effect tyre clearance as much as I first thought. And apparently if you want perfection, you buy a Mercedes!!!
http://www.youtube.com/watch?v=U3ux-eGJoP0&feature=related
http://www.youtube.com/watch?v=U3ux-eGJoP0&feature=related
"BenzBoy: It does not matter how wide a tyre / rim combination is, so long the offset for the rim is OK. For zero offset steering (whch the W116 has,) the centre of the contact patch of the tyre on the road must pass through the axis of the king pin or what serves as that axis."
Right - I see.
OK try this then:
I am advised of the following - If you're interested simply in the area of contact for tyres I believe the calculation is straightforward and easily derived on the back of an envelope.
If w = gross weight of vehicle in pounds
p = tyre pressure in PSI
n = Number of tyres
c = contact area per tyre (in square inches)
then c = w/np
If the front and rear tyres run different pressures the above formula could get complicated but I haven't derived it yet so I can't say for sure.
Even further - http://en.wikipedia.org/wiki/Slip_angle and http://www.performancesimulations.com/fact-or-fiction-tires-1.htm
Nothing is as simple as it first seems.
Regards,
Brian
From what I now understand the contact area per tyre does not change if you fit wider tyres. It's the shape of the patch that changes....
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