mu sunny bottoms out on the bump stops when i launch it but its only a standard a14
| OZDAT http://www.ozdat.com.au/forum/ |
|
| 610 bouncing on take off at drag strip http://www.ozdat.com.au/forum/viewtopic.php?t=32635 |
Page 1 of 3 |
| Author: | Super [ Fri Apr 25, 2014 12:35 pm ] |
| Post subject: | 610 bouncing on take off at drag strip |
Hi all, Im in the process of making changes to my car to get the absolute best ET out of it. After having played with diff ratios and tyre sizes and sorted that part of it out. Im now in the process at looking at the suspension side of things. I noticed that car was bouncing around on take off as though the suspension was bottoming out and this was confirmed in the video... which Im putting down to excessive power. Heres the video Im running KDRL-02 King springs at the back and this was an improvement from the KDRS-02 springs I used previously. Im thinking of getting springs that are stiffer again to what I have now to counter the power surge on the take off and reduce the car from bottoming out. opinions?? What springs are available that would fit a 610 with a higher spring constant? |
|
| Author: | lampy [ Fri Apr 25, 2014 7:19 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
Looks like your shocks are not dampening your springs enough. What shocks do you have and what spring rate |
|
| Author: | nick [ Fri Apr 25, 2014 10:08 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
The springs compressing is not necessarily a bad thing as it aids in weight transfer onto the rear tyres but can be bad if this causes excessive rear camber which will tilt the tyre and lose contact area with the ground or alternatively if the springs rate of compression/rebound is not dampened enough it will bottom out on the bump stops hard and bounce back etc. Many irs drag cars raise the rear suspension height so camber starts out positive (looks weird i admit) at standstill but when launching it doesnt go neg as much. This will also gain some travel back in the rear end so it wont hit the bump stops as quick. As Lampy said i'd look at adjustable (2way?) shocks to better control the spring compression and rebound. Try going back to a softer spring with these adjustable shocks too as in theory you should get better control. A big rear swaybar and nolathane bushes on control arms and rear crossmember is supposed to help as does a slick with a soft sidewall and the correct tyre pressure... |
|
| Author: | Super [ Sat Apr 26, 2014 10:50 am ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
Im using KYB Mono gas Shock absorber and KDRL-02 King springs 615lb linear rate. I will also correct that my previous set was not KDRS-02... It was something even lower than the KDRL-02 which were supplied by Datsport when the rear end was purchased. I will try to get my hands on a set of KDRS-02's or even KDRS-03's which should give better height for the 610, but what Shock Absorber do you guys recommend? the 610 is currently running in the mid 11's and would really like to see this car break though to the 10's FeZ |
|
| Author: | lampy [ Sat Apr 26, 2014 11:39 am ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
615lbs is a very low spring rate. Maybe you are bottoming out on the bump stops. i would look at getting a smaller bump stop or try a heavier spring. I have completely removed the bump stops in my circuit race 1600, but i run a much heavier spring rate eg 1200 lbs If you have adustable camber and toe i would take the spring out and jack the trailing arms to about where the trailing arms sit on full launch. At that point i would say for drag racing you would want minimal toe or camber to get full traction. As you gain speed the squat will reduce and then the tyres can cope with slight postive camber |
|
| Author: | nick [ Sat Apr 26, 2014 3:07 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
I wouldnt recommend taking the bump stops out or modify the bump stops by making them shorter in this instance. This would make the cv's/uni's potentially operate at greater angles when launching hard which will break them easier under power. Try KONI shocks as ive seen they have at the very least rebound adjustable shocks or even consider rear coilovers by Ermish Racing, T3 or Ground Control etc. They seem pretty trick and have multiple adjustment settings. Traction doesnt seem to be the issue so dont worry too much about camber and toe just yet... |
|
| Author: | Super [ Sun Apr 27, 2014 5:04 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
I might have a set of heavier springs... Ill check and and give it a go. But these coil over setups look great... And would be ideal to make adjustments Will the mounting point of the shock be able to handle the weight if the car though when the spring is removed? or does it need strengthening ? Ground Control specifies that the upper mount they provide is designed to carry the weight of the car, but this confuses me as the coil over will need to mount to the original shock mounting point which is not designed to carry the whole weight of the car. Has anyone used these coil over setups and can give insight FeZ |
|
| Author: | sutho510 [ Sun Apr 27, 2014 9:12 pm ] | |
| Post subject: | Re: 610 bouncing on take off at drag strip | |
Will the mounting point of the shock be able to handle the weight if the car though when the spring is removed? or does it need strengthening ?
Alot of people ask the same question because that point was only made to take the shock on and not a spring and shock
Ground Control specifies that the upper mount they provide is designed to carry the weight of the car, but this confuses me as the coil over will need to mount to the original shock mounting point which is not designed to carry the whole weight of the car. Has anyone used these coil over setups and can give insight FeZ |
||
| Author: | nick [ Sun Apr 27, 2014 11:04 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
The top of the shock has a reinforcing plate there which is fairly thick. No issues come to mind that ive read of this being damaged yet but if you push the boundaries then you may have to do further reinforcing there. Especially if you will be relying on a coilover assy bump stop to limit squat and not the std bump stops on the swing arm... |
|
| Author: | SR20Datsun [ Mon Apr 28, 2014 11:51 am ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
Where abouts are you located? I would recommend some double adjustable shocks from ToPerformance (Koni's). I can give you the part number if you are interested? You need to change the spring rate to suit the shock (or vice versa). If Baz supplied springs with the shocks, then you would assume the rate supplied would match the shocks. Try and find a spring that is similar in rate, but higher/lower to suit your ride height. Make sure the spring is captive throughout the travel. You can modify the bump stops (only if you check the extra travel doesn't foul anything and your joints still rotate UNDER POWER) I wouldn't modify the bump stops until you figure out what is happening. |
|
| Author: | k-man 79 wagon [ Mon Apr 28, 2014 3:55 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
mu sunny bottoms out on the bump stops when i launch it but its only a standard a14
|
|
| Author: | DATO4 [ Mon Apr 28, 2014 10:20 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
start with a heavier spring. call wholesale suspension in penrith, tell them you want an adjustable koni shock to suit the spring you choose. I had this done, i now have a modified and adjustable koni yellow to suit the datsport 1100lbs springs. was around $300 from memory. I have a 1600 though. some angles to think about..... http://youtu.be/QnSr8fr6ZJY |
|
| Author: | JK [ Tue Apr 29, 2014 1:08 pm ] | |
| Post subject: | Re: 610 bouncing on take off at drag strip | |
start with a heavier spring. call wholesale suspension in penrith, tell them you want an adjustable koni shock to suit the spring you choose. I had this done, I now have a modified and adjustable koni yellow to suit the datsport 1100lbs springs. was around $300 from memory. I have a 1600 though.
DATO4, hows your axle tramp/wheel hop?. My setup is similar to what you've described. I have revalved/shortened Koni Yellow (commodore), combined with 1000+lbs rear springs. i sometimes get quite bad axle tramp when launching. Im thinking trying some different shocks to see if it improves - unless its something else causing it... |
||
| Author: | DATO4 [ Tue Apr 29, 2014 5:20 pm ] |
| Post subject: | Re: 610 bouncing on take off at drag strip |
My koni yellows aren't shortened but are also revalved commodore shocks. However I have adjustable rebound, maybe swap for the same shock but with adjustable rebound. This should help stop the tramp |
|
| Author: | JK [ Tue Apr 29, 2014 6:52 pm ] | |
| Post subject: | Re: 610 bouncing on take off at drag strip | |
My koni yellows aren't shortened but are also revalved commodore shocks.
Sound like you have the same shocks as me. Adjusting the rebound doesn't seem to help the problem. You have no problems with those springs and tramp?
However I have adjustable rebound, maybe swap for the same shock but with adjustable rebound. This should help stop the tramp |
||
| Page 1 of 3 | All times are UTC+11:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|