Tamiya Hornet Evo understeer

[desmobob]

I just ran the first battery pack through my new Hornet Evo build. I have a Tamiya Sport Tuned motor on the way but I'm satisfied with the stock motor performance.

I'm new to 2WD buggies and I think it's a fun vehicle so far. The only thing I'd like to improve on is the understeer.

For a 2WD buggy, I expected I'd struggle with oversteer and was pleased that the Evo didn't ground loop every time I was a little over-eager with the throttle. The understeer is quite a bit more than I think I'd like though. The modifications Tamiya made to "modernize" the Hornet Evo results in a very large rear weight bias, increasing the understeer the original is already known for.

The kit's rear end builds with plenty of toe-in. Tamiya recommends two-in on the front. I was always of the belief that an off-road vehicle should have rear toe-in and front toe-out, so I built it with some front toe out. Was that a mistake? I'm going to add some weight to the nose of the chassis. Does that sound reasonable?

I'm not a vintage racer and will just do a little casual dirt lot bashing with the buggy, so it's fine the way it is. I'm just wondering if I can tune it so it's a little bit more fun...

 

[Ritz413]

I just ran the first battery pack through my new Hornet Evo build. I have a Tamiya Speed Tuned motor on the way but I'm satisfied with the stock motor performance.

I'm new to 2WD buggies and I think it's a fun vehicle so far. The only thing I'd like to improve on is the understeer.

For a 2WD buggy, I expected I'd struggle with oversteer and was pleased that the Evo didn't ground loop every time I was a little over-eager with the throttle. The understeer is quite a bit more than I think I'd like though. The modifications Tamiya made to "modernize" the Hornet Evo results in a very large rear weight bias, increasing the understeer the original is already known for.

The kit's rear end builds with plenty of toe-in. Tamiya recommends two-in on the front. I was always of the belief that an off-road vehicle should have rear toe-in and front toe-out, so I built it with some front toe out. Was that a mistake? I'm going to add some weight to the nose of the chassis. Does that sound reasonable?

I'm not a vintage racer and will just do a little casual dirt lot bashing with the buggy, so it's fine the way it is. I'm just wondering if I can tune it so it's a little bit more fun...

Weight on the nose sounds like a good play to me. It sounds like you are fighting push where the rear has so much traction it wants to go straight and fights the turn cutting down on cornering. The motor upgrade might help too, where a little more power will give you some ability to break the back end loose and swing it around a little easier.

 

[desmobob]

Weight on the nose sounds like a good play to me.

I added 1.25oz of lead as far forward as possible. Adding the thin thickness spring preload spacers brought the ride height back up to where it was. I'm using 45wt shock oil. I'm running the rear shocks with two spacers on each: the thickest and the medium thick. This has the chassis sitting very close to level at rest instead of sagging in the rear like it did with no adjustments.

I just ran it after adding the nose weight. It felt like it turned a bit better, at least on rough pavement, but it also seemed to have a slow, wallowing bounce over the dips and humps. I may try removing a half ounce of weight. I also wondered about the lack of tire foam in the soft rear tires being at least part of the wallowing (if that's the right choice of word) with the extra weight.

Are there tire foams available for those weird Tamiya spiky tires? I'm just a basher and I'd like to keep the original look of the kit rather than fitting new wheels/tires.

 

[Ritz413]

I added 1.25oz of lead as far forward as possible. Adding the thin thickness spring preload spacers brought the ride height back up to where it was. I'm using 45wt shock oil. I'm running the rear shocks with two spacers on each: the thickest and the medium thick. This has the chassis sitting very close to level at rest instead of sagging in the rear like it did with no adjustments.

I just ran it after adding the nose weight. It felt like it turned a bit better, at least on rough pavement, but it also seemed to have a slow, wallowing bounce over the dips and humps. I may try removing a half ounce of weight. I also wondered about the lack of tire foam in the soft rear tires being at least part of the wallowing (if that's the right choice of word) with the extra weight.

Are there tire foams available for those weird Tamiya spiky tires? I'm just a basher and I'd like to keep the original look of the kit rather than fitting new wheels/tires.

45wt at least up front seems heavy to me. Stiffer front springs could also help with steering response.

 

[desmobob]

Thanks. I just ordered the Tamiya 54465 spring set.

 

[RustyUs]

The modifications Tamiya made to "modernize" the Hornet Evo results in a very large rear weight bias, increasing the understeer the original is already known for.

Thanks. I just ordered the Tamiya 54465 spring set.

I hope that spring set has softer front springs. Seems to me you already know the buggy's design gives way to limited steering/weight adjustment. Soften up the front end to get more weight transfer to some grippier front tires. I don't know how much room the battery compartment has. Is there any wiggle room while using a NiMh stick pack? A shorty 2S LiPo all the way forward on the chassis is probably outside of "things to consider". Enjoy it the Hornet for what it is.

 

[joerzr]

Weight on the nose sounds like a good play to me. It sounds like you are fighting push where the rear has so much traction it wants to go straight and fights the turn cutting down on cornering. The motor upgrade might help too, where a little more power will give you some ability to break the back end loose and swing it around a little easier.

Does the kit include spare parts to add Tamiya's wheel set from DT-02, 03, and 04 chassis? I think the conversion parts are there. The new wheels accept modern size buggy tires that will improve handling/turning. You can also use Tamiya rubber...the tires from Holiday Buggy are good in dirt. And that kit has nice bright yellow wheels that I'm refering to. Check them out. I have seen Tamiya wheels + tires on Amazon.
I agree, weight in front of chassis will help. And try the recomended toe in...maybe it will improove turning and it's free.

 

[xjtorc]

Soften the front and stiffen the rear. Understeer happens because weight isn't being transferred to the front end. Also, there's always the possibility that poor suspension geometry creates a side effect of the chassis that just can't be beat by proper suspension tuning...common in the vintage buggies and trucks.

Are there tire foams available for those weird Tamiya spiky tires? I'm just a basher and I'd like to keep the original look of the kit rather than fitting new wheels/tires.

eBay Link

You really have to search for them, but they're out there.