2WD wheels on 4WD????

Welcome to RCTalk

Come join other RC enthusiasts! You'll be able to discuss, share and private message with other members of our community.

bill_delong

RCNT Qualifier
Military Veteran
Build Thread Contributor
Messages
139
Reaction score
110
Location
Austin, TX
RC Driving Style
  1. Racing
I know this is not a new concept. I have already clarified the rules with ROAR where they only set maximum wheel dimensions, there are no minimums.

Current 2WD carpet tires are now based on a "Slim" design which shaves off a significant amount of weight (i.e. rotating mass).

So I decided to do a side by side comparison with a set of 4WD ProLine "Prisms" versus Raw Speed "Fast Forwards" on my 13.5 wheeler where anything you can do to reduce rotating mass is essential in being competitive for stock racing.

1672880144807.png



1672880295752.png



4WD Prisms weigh in at 216g

1672880347087.png


Fast Forwards weigh 153g

1672880383250.png



That's a total of 63g shaved of rotating mass!

Tire Diameter from left to right in following pic:
PL Prism (Rear) = 86mm
RS Fast Forward (Rear) = 82mm
PL Prism (Front) = 84mm
RS Fast Forward (Front) = 76mm

1672880450671.png


Average temps coming off track after 9 min with Prisms was 160°F
Average temps coming off track after 9 min with Fast Forwards is 120°F

Note that acceleration is notably more powerful and I had to adjust my ride height (and gearing) to account for the new diameter in wheel sizes. Grip was amazing with a very stable and easy to drive, the 2WD wheels are a pinch less "twitchy" than traditional 4WD wheels, but lap times are faster due to the improved acceleration. Most importantly, there is no detectable loss of punch toward the end of the run due to improved efficiency as well.

I made it a point to test 2WD wheels where Raw Speed tends to offer a little more lip in the hex than other brands of 2WD wheels where I have had issues with stripping out 2WD hexes on the wheels in the past which is why I stopped using them. On the current set of Raw Speed 2WD Slim wheels I have a combined total of 45 min of track time with plenty of wall taps and hitting pipe at full throttle as seen by the scuffs on the wheels in the photos to confirm no stripped hexes yet!
 
Last edited:

DavidB1126

RCNT Addict
Build Thread Contributor
Messages
728
Reaction score
676
Location
Baltimore
RC Driving Style
  1. Bashing
  2. Racing
Good information. I will try different 2wd/4wd wheel/tire combinations for my freshly built B74.1 (have the dirt version but planning to race on both clay and carpet)

Thanks for sharing!
 

bill_delong

RCNT Qualifier
Military Veteran
Build Thread Contributor
Messages
139
Reaction score
110
Location
Austin, TX
RC Driving Style
  1. Racing
Good information. I will try different 2wd/4wd wheel/tire combinations for my freshly built B74.1 (have the dirt version but planning to race on both clay and carpet)

Thanks for sharing!
Glad to help, I have ran standard 2WD wheels on clay in the past with very good results, one of the locals got butt hurt and claimed I was cheating, so I went to ROAR and they graciously replied back explaining it was perfectly fine. Not sure about the hexes on the AE wheels, but you may need to stretch the tires to fit on 4WD wheels if the hexes strip on the 2WD wheels. I was stripping the TLR22 wheels myself at the time when I last ran them on clay a few years back.
 

Bogda89

RCNT Talkaholic
Messages
237
Reaction score
139
How smaller diameter affect the ride. Do you use thinner center diff oil to allow the difference in wheel speed between front and rear?
 

Greywolf74

I'M TO BLAME!
Lifetime Supporter!
Supporter
Hospitality Award
Build Thread Contributor
Messages
14,553
Reaction score
6,952
Location
Ohio
RC Driving Style
  1. Bashing
I know this is not a new concept. I have already clarified the rules with ROAR where they only set maximum wheel dimensions, there are no minimums.

Current 2WD carpet tires are now based on a "Slim" design which shaves off a significant amount of weight (i.e. rotating mass).

View attachment 157830


So I decided to do a side by side comparison with a set of 4WD ProLine "Prisms" versus Raw Speed "Fast Forwards".

View attachment 157831


4WD Prisms weigh in at 216g

View attachment 157832

Fast Forwards weigh 153g

View attachment 157833


That's a total of total of 63g shaved of rotating mass!

Tire Diameter from left to right in following pic:
PL Prism (Rear) = 86mm
RS Fast Forward (Rear) = 82mm
PL Prism (Front) = 84mm
RS Fast Forward (Front) = 76mm

View attachment 157834

Average temps coming off track after 9 min with Prisms was 160°F
Average temps coming off track after 9 min with Fast Forwards is 120°F

Note that acceleration is notably more powerful and I had to adjust my ride height to account for the new diameter in wheel sizes. Grip was amazing with a very stable and easy to drive, the 2WD wheels are a pinch less "twitchy" than traditional 4WD wheels, but lap times are faster due to the improved acceleration. Most importantly, there is no detectable loss of punch toward the end of the run due to improved efficiency as well.

I made it a point to test 2WD wheels where Raw Speed tends to offer a little more lip in the hex than other brands of 2WD wheels where I have had issues with stripping out 2WD hexes on the wheels in the past which is why I stopped using them. On the current set of wheels I have a combined total of 45 min of track time with plenty of wall taps and hitting pipe at full throttle as seen by the scuffs on the wheels in the photos to confirm no stripped hexes yet!
I'm shocked at how much cooler the temps are from just that one change.

My first thought was "what about handling?" but it sounds like its handling like a dream. Great info!
 

WickedFog

Starter of too many projects
Supporter
Excellence Award
Hospitality Award
Build Thread Contributor
Messages
9,167
Reaction score
10,544
Location
Terre Haute, IN
RC Driving Style
  1. Bashing
  2. Crawling
  3. Scale Builder
I'm shocked at how much cooler the temps are from just that one change.

My first thought was "what about handling?" but it sounds like its handling like a dream. Great info!
It essentially lowered the final ratio, same as a pinion change would. It has a lot more underdrive on the front with the 4mm change in the rear, but an 8mm change in the front. So the front tires would essentially be putting on the brakes so to speak. So I can see that affecting handling. But I would be curious if it has any noticeable understeer? Which begs the question... can you buy different gear ratios for the front diff? That would be fun to play around with to see if you can get a more optimal underdrive/overdrive ratio in the front. Very interesting.
 

bill_delong

RCNT Qualifier
Military Veteran
Build Thread Contributor
Messages
139
Reaction score
110
Location
Austin, TX
RC Driving Style
  1. Racing
How smaller diameter affect the ride. Do you use thinner center diff oil to allow the difference in wheel speed between front and rear?
Yeah I had to adjust the shock collars on both the rear and front to get it back to proper ride height, took nearly 20 turns on the front to level out, ha!

I ran same diff fluids 10-60-5 and the car handles amazing
It essentially lowered the final ratio, same as a pinion change would. It has a lot more underdrive on the front with the 4mm change in the rear, but an 8mm change in the front. So the front tires would essentially be putting on the brakes so to speak. So I can see that affecting handling. But I would be curious if it has any noticeable understeer? Which begs the question... can you buy different gear ratios for the front diff? That would be fun to play around with to see if you can get a more optimal underdrive/overdrive ratio in the front. Very interesting.
if anything the car is more stable and easy to drive, definitely no issue with under steer, yes there's a different gear ratio available with the mini-truggy version of this platform but I don't feel the need to test those parts. I'll be retiring this car once HB releases the D4 Evo3, I will be racing that platform this season.

-------------------------

So here's the actual results, last race day I had with the Prisms had net a fast lap of 21.3 where a driver of equal skill "JETT" had hit a 21.8:
https://trc.liverc.com/results/?p=view_race_result&id=3969654

JETT out qualified me this past weekend on the 1/8 track. I would manage to get around JETT (Jon Bennett) in the mains, so you can see we go back and forth on skill:
https://trc.liverc.com/results/?p=view_multi_main_result&id=527298

side note on the result sheet, yes that is the same Jared Tebo and I had the pleasure of looking over his soon to be released factory ride :)

Here's my final test session with the Fast Forwards which hit a fast lap of 20.4:
https://trc.liverc.com/practice/?p=view_session&id=12737635

Note that my average top15 laps were 21.3 which was my fast lap with the Prisms, ha!

LOTS of variables all around so it's like comparing apples to oranges, but as far as I'm concerned, 2WD wheels for spec racing is definitely an advantage!
 
Last edited:
Top