| Author | Message | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1104 Registered: 10-2006 Posted From: 66.82.162.16  Rating: N/A |
http://americamovesbytruck.com/rollingresistance.php Here is one site that lists rolling resistance for some tire mfg. FF | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 403 Registered: 9-2006 Posted From: 209.156.24.114  Rating: N/A |
Usually with any advantage there is a disadvantage. SO.... What do you loose in tire performance when you decrease the rolling resistance? . | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1105 Registered: 10-2006 Posted From: 66.82.9.80 Rating: N/A |
What do you loose in tire performance when you decrease the rolling resistance? Mostly its a matter of cost,the good stuff does cost more , and weather its a good deal on a 10,000 mile a year camper is up to you. All the tires will rot off in bus camper service , way before 200,000 miles are run. WE prefer steer tires on every wheel , smoother and loads quieter than ribbed. FF | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1019 Registered: 1-2003 Posted From: 67.142.130.39  Rating: N/A |
You lose traction. Lower rolling resistance also means longer stopping distance, less cornering ability, and more slipping of drivers on poor surfaces such as dirt, mud, snow, ice, and slick roads. As you so astutely observed, everything is a trade-off; it is not strictly a matter of money as Fred suggests. I would not trade my block-tread traction drivers for all the tea in China (Bridgestone M711's, RR index 154).
Steer tires are rib tires. I'm guessing you meant to say "traction" instead. Ribs run with the circumference of the tire (or with the direction of travel, if you prefer); sipes run across the tread, or at an angle to the direction of travel. Lugs have sides in both directions. Actually, most tires have ribs, but a "rib tire" is one in which the ribs are unbroken by sipes or lugs, usually found on steer or trailing positions. "All-position" tires are also generally considered rib tires, but the ribs have crenellations (a saw tooth pattern) to promote traction. -Sean http://OurOdyssey.BlogSpot.com (Message edited by Sean on March 11, 2010) | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1108 Registered: 10-2006 Posted From: 66.82.9.49 Rating: N/A |
"You lose traction. Lower rolling resistance also means longer stopping distance, less cornering ability, and more slipping of drivers on poor surfaces such as dirt, mud, snow, ice, and slick roads. " Most of our coaches are far from spinning the wheels on a dry pavement start , at least my Sportscar is. Breaking is frequently limited by the brake treadle valve assembly installed. Line pressure is seldom fed to the brakes as flat spots are possible (dry to wet to dry pavement ). While I do have the Sportscar of Coaches , drifting round curves , all 6 wheels in a controlled slide is seldom my style. On snow and ice tread pattern is as important (and even more so tire pressure) than the hysterisis if the casing. Only traction problems I have seen were from slushpump coaches bugging out from covered toll booths. A rear wheel set would loose traction on all the oil in the covered area , and SNAP! when getting onto cleaner pavement at full throttle with loose torque converter.. FF | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 404 Registered: 9-2006 Posted From: 209.156.24.114 Rating: N/A |
My thought process.... (right or wrong) You will have less roll resistance if you have: 1. higher tire air pressure 2. harder tire composition 3. less contact area between tire and road SO,,, What does the tire manufacturer do to get a low roll resistance? 1. require higher tire pressure? (not likely) 2. use a harder rubber composition? [a. harder rubber in the sidewall?] [b. harder rubber in the tread area?] 3. design the tire to have less contact with the road? [a. narrow tire tread area?] [b. wider tread grooves/less rubber to contact road?] In this thought process it all comes back to what seems to be the same end result. to get less roll resistance you give up traction. My best experience with tires is with my motorcycle. 1. I can get a long lasting tire but I will loose grip on the road. 2. I can get a tire that grips the road like my Aunt Minnie pinches pennies but they will only last one season. FYI: I have Toyo M122 tires at all 4 corners of the bus. This tire is not on the list... . (Message edited by zimtok on March 12, 2010) | ||
| Justin Burie (Justinb)
Registered Member Username: Justinb Post Number: 10 Registered: 1-2010 Posted From: 209.254.23.194 Rating: N/A |
Another factor in rolling resistance is lug flex. As you are applying torque to the ground with lugged or cross-cut tires, thise lugs will flex as they come into & out of contact with the road surface. The deeper the tread the greater flex & the greater the rolling resistance. A set of 29/32" deep lug tires with soft rubber is akin to throwing an anchor out the back of your vehicle. A set of 21/32" deep ribbed tires with hard rubber is akin to off roading on racing slicks. If you are a snow-bird & stay on prepared roadbed surfaces, nothing is needed greater than a Michelin XZE type of tire. Thin Siping a ribbed tread will gain a nice advantage on icy roads in the winter. I have demoed school buses on snow closure days (12"+) with Michelin XZEs all the way around & had no problems getting through the snow. Even in the unplowed bus lots. To reduce rolling resistance go to a low-pro type of tire to reduce contact surface. Warning: the air chamber is smaller. Lo-Pro tires do not like 80mph on 90f days. To really reduce rolling resistance, a drive tire like the Michelin "X-1" series super single (445 & 455 profile)is an excellent tire & looks really cool to boot. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1865 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
Thanks Fred for that site. Sometimes low rolling resistance can also be accomplished with a premium tread compound aka more costly. BTW those numbers don't mean as much unless a high number is compared with a low number on our coaches; 50 points could only be a tenth of a mile per gallon. I'm not saying that a tenth isn't significant on a 6 mile per gallon coach, just what 50 points on that chart mean.I didn't thoroughly check out site whether they might have had some real world test mpg results. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1022 Registered: 1-2003 Posted From: 67.142.130.32 Rating: N/A |
John, The data on that site came from Michelin. I would bet money that they do have real world test results, but I would also guess that they consider the data proprietary and have not published it. FWIW. -Sean http://OurOdyssey.BlogSpot.com | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1110 Registered: 10-2006 Posted From: 66.82.162.14 Rating: N/A |
Someone was kind enough to post this , when I was attempting to select a new rear axle ratio for the VL. You will see rolling resistance is a large part , and a 50% reduction in rolling resistance would be very worthwhile. "Here is why those big hills slow us down so much. Minimum NET HORSEPOWER (NHP) to maintain speed on a grade NHP= MPH x (rolling resistance + grade) x GVW divided by (driveline efficincy x 37,500) or NHP = (MPH x R X GVW) divided by (E x 37500) assummed (E) - Drive line eff. = .85% (R) - rolling resistance = 2% + grade 6% MPH - 50 mph GVW - 10,000 lbs Gross vehicle weight then NHP = 50 x 8 x 10,000 divide by .85 x 37500 NHP = 125 at 50 MPH -> 125 Horse Power at 60 MPH -> 150 Horse Power at 70 MPH -> 175 horsepower WE used the formula to attempt to stay in OD on 3% (common) grades , and only downshift on the steeper hills. FF | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 152 Registered: 2-2009 Posted From: 66.122.182.221  Rating: N/A |
So Fred, what rearend ratio did you end up with? | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1111 Registered: 10-2006 Posted From: 69.19.14.38 Rating: N/A |
I chose a 2.94 , which is as high as I dared to go. The coach should only be 25,000lb when completed and I want to cruise at 65-70 at about 1400 for economy. The "ace in the hole" is the old tires are 12R22.5 stoopidly huge for a coach of this weight , but probably the largest diameter short of 24.5s This will allow some testing ,the only nearby "hill" in FL is the Sunshine bridge, so at a buck a run some data will be useful. We have smaller 11r's , so if she bogs on the hills the smaller tire will be tested. If the numbers are way off the 12R 22.5 low pro are really small and will be about the same as choosing a 3.08 rear. Will be an interesting test program. The best is if she takes normal slab hills at under 10lbs of boost, 12+ mpg should result. FF | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1832 Registered: 12-2000 Posted From: 76.71.102.111  Rating: N/A |
I'm looking forward to the results. A lot of thinking has gone into this upgrade. Everything is a compromise, stock or custom. happy coaching! buswarrior | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1319 Registered: 5-2001 Posted From: 65.74.67.7 Rating: N/A |
The manufacturers are claiming that there is no compromise in tread life or traction in the newer low energy tires. Wikipedia has an interesting entry on rolling resistance. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| joe padberg (Joemc7ab)
Registered Member Username: Joemc7ab Post Number: 391 Registered: 6-2004 Posted From: 66.38.159.33 Rating: N/A |
Fred How far have you progressed on your project now? Joe. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1112 Registered: 10-2006 Posted From: 66.82.162.10 Rating: N/A |
How far have you progressed on your project now? About 1500lbs of metal renewed for the massive rust , with about 1/2 of that being reinforcement . The stock 6-71 had 1/2 the HP and torque of the Ser 50 , and the Jakes will create torque in the "wrong" direction. The new rear axle is in place. The engine tranny beds are going in . The engine is on the bench for new bearings as a precaution and the Jakes are going on, the new waste gate turbo is going on . The proper bell housing is in hand , and most of the parts to get the ZF hooked to the DD 50 are in hand. A mock up combo has been fitted to the frame , so the drive shaft folks can get their measurements. Insulation (blue board) is being fitted and the skin is only a couple of weeks from going back on. The Cat 1160 (3208) and 6 speed Allison and old rear are out and for sale $1500. FF | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 29 Registered: 1-2010 Posted From: 68.151.248.141 Rating: N/A |
Fred I see in your last post that you are going to use blue board insulation in your coach. I am getting to the point of insulation as well and would like to hear your reason for picking blue board over other products. I have been looking into the spray in foam. Any comment? Les | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 507 Registered: 10-2003 Posted From: 66.165.176.62  Rating: N/A |
Fred, You need to post some pictures of the process. I would love to see the progress. | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 340 Registered: 12-2000 Posted From: 72.187.35.208  Rating: N/A |
Fred, The Sunshine Skyway is hardly a test. It is not as steep as it looks, less than 200' rise in almost a mile. I have topped it in forth gear in a 4104, no where near ready to shift. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1113 Registered: 10-2006 Posted From: 69.19.14.15 Rating: N/A |
I have topped it in forth gear in a 4104, no where near ready to shift. Yes my Sportscar does the same , the question is will the speed hold or decay as we run up the big speed bump. I am getting to the point of insulation as well and would like to hear your reason for picking blue board over other products. I have been looking into the spray in foam. Any comment? MY experience is in marine refrigeration and blue board may not have the R value of other materialm but it DOES NOT ABSORB WATER. The Isocyanurate (sp?) and can spray foam do absorb water and as this is a tube framed structure , constant wet will mean constant rust and a departing frame. FF | ||
| Justin Burie (Justinb)
Registered Member Username: Justinb Post Number: 11 Registered: 1-2010 Posted From: 209.254.23.194 Rating: N/A |
That SRS50 will feel like a monster compared to the 6-71. I'm not real familiar with the Z-F. What is the top gear ratio? What tires & rear axle are you planning on? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1867 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
check the other board; they just had a serious discussion of foam vs. board | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1114 Registered: 10-2006 Posted From: 66.82.9.56 Rating: |
check the other board; they just had a serious discussion of foam vs. board What "other " board? FF | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1115 Registered: 10-2006 Posted From: 66.82.162.13 Rating: N/A |
"I'm not real familiar with the Z-F. What is the top gear ratio? What tires & rear axle are you planning on?" The latest big truck fuel economy thinking is to use a 10 speed with no OD. The losses in the tranny of the OD are therefore avoided , straight thru is most efficient. This gets a 2.64 rear on OTR trucks that will run 80,000lbs and even the newest aerodynamic cabs are still 12 ft high and draggy . The ZF is a slush pump but coaches are light , even the tanks are only 1/2 the weight of a truck so only 5 speeds is needed. The OD is .85 or so , the rear chosen of 2.93 x .85 gives an effective rear ratio of 2.48. This is even higher than the OTR pull , but the VL 100 is low sleek and perhaps only 25,000 lbs or so all done. The DD 60 trucks run 1250rpm to 1400rpm as the "sweet spot" although with high fuel costs some will only run 60mph. WE will tinker with the wheel and tire size to see if we can get the sweet spot at 70 . Instead of super singles , which are costly as heck , I am contemplating using the front extra wide wheels off a cement truck as rear wheels. Since these are made for ground clearence , it would only work IF large diameter tires can be pulled , there doesn't seem to be Low Profile for this size/service wheel. Still figgurin', but an actual road test will point in the direction to go. FF | ||
| Justin Burie (Justinb)
Registered Member Username: Justinb Post Number: 12 Registered: 1-2010 Posted From: 209.254.23.194 Rating: N/A |
When I was in the truck business, my customers did well with a 3.42:1 & a .73:1 top gear. This puts you at 2.49:1 total. Pretty good figuring there. The ZF should be a full lock-up, yah? That'll keep you from losing anything to a slush box like the old AT/MT/HT boxes. Given what you've got so far, an 11R22.5 drive tire will work nicely to fit your performance needs. While the areo trucks have a 13'6" profile, you are effectively pushing a brick down the road. Spinning the SRS 50 about 1450-1500 at 70 would be a good thing. Comparison: XDN2.....11R22.5.....496 rev/mile X1XDN2..455/55R22.5..491 rev/mile Qty 4 XDN2 11R22.5 Qty 4 22.5x8.25 Wheels (steel?, alum?) may have to change hubs out for HP-10 Qty 2 X1XDN2 455/55R22.5 Qty 2 22.5x14 - Ya know they'd hafta be alum. ;) must change hubs out to HP-10 Another option would the XZE version of either tire. Less Rolling resistance & a more pliable compound to resist checking/cracking over time. They also take manuevering much more gracefully than harder compound tires. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1116 Registered: 10-2006 Posted From: 69.19.14.41 Rating: N/A |
The XZA is 490 rpm or 39.2 diameter. It gives in OD 1100 52, in 4th .....44 1200 57, ............. 48 1300 62, ............. 51 1400 67, ............. 55 1500 72, ............. 59 1600 76, ............. 63 1700 81, ............. 67 1800 86, ............. 71 SO there should be some good hill climbing ability in 4th if needed , with little slowdown. With the now fitted tall 12R22.5 it will be an interesting experiment to see how she can climb in OD. Should the engine not be as powerful as planned Lo Pro with a 34.4 diameter XZE would give 54 at 1300 or 67 at 1600 and climb tall buildings! FF | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1130 Registered: 10-2006 Posted From: 66.82.9.15 Rating: N/A |
A concept the coaches with Tag axles might wish to copy from the truckers, is to install trailer tires on the tags. Trailer tires have the lowest rolling resistance of all. Some of the trucks will drive with the tags lifted , when the weight limits allow this. Might be a coach solution to lift the tag on the roads where the coach will make the wheel loading rules. FF |
