Quote from: tets on October 16, 2020, 18:03that looks like it's going to be a right thing!!

A right mess maybe!

Quote from: 1979scotte on October 16, 2020, 18:53Are they going to allow that on track?
You'll scare the other punters.

I hope so. Plan is to build some sort of 'bumpers' around the wheels so they're not open...

Quote from: Chilli Girl on October 16, 2020, 19:23Fascinating to see a skeleton 2.  Never seen it like that before.

They are quite interesting eh? I've seen one or two MR2 'karts' on the web, it's more common with MX5s though.


In the quest for cheap speed, I went on the hunt for smaller wheels. This will drop the centre of gravity without upsetting the suspension design, and effectively reduce the gearing which is the same as adding poowwweeerrrr. 10% in fact, if I could shoehorn some 195/45/14s on there as opposed to the stock 205/50/15s. Not insignificant...

I have a set of 13s that actually JUST fit, but they are worth as much as the car and probably too light, so not really appropriate sadly.

So, that led me to Facebook classifieds, and a set of unloved MX5s wheels a couple of miles away. All 4 tyres knackered, but the wheels actually in pretty good nick, 14" and only £50, so worth a punt. Armed with a tape measure, I had a check of the inner bore and thought they might clear - worth a punt anyway, and deal with any problems later 

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Picking them up revealed a funny smell. I have a suspicion the previous owner's dog had been using the stack as a pissing post! Still, a quick wash sorted that, then time for the moment of truth...

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They only bloody fit! Literally a mil to spare. I had to pull the wheel weights off to get the rears to go round, and even then the sticky residue scrubs the caliper!

Now on the lookout for tyres, not much choice in that size and all road tyres (which is what I wanted), so good value, fun in the dry, and safe in the wet.

Quote from: AdamR28 on October 19, 2020, 18:34

Quote from: tets on October 16, 2020, 18:03that looks like it's going to be a right thing!!

A right mess maybe!

Quote from: 1979scotte on October 16, 2020, 18:53Are they going to allow that on track?
You'll scare the other punters.

I hope so. Plan is to build some sort of 'bumpers' around the wheels so they're not open...

Quote from: Chilli Girl on October 16, 2020, 19:23Fascinating to see a skeleton 2.  Never seen it like that before.

They are quite interesting eh? I've seen one or two MR2 'karts' on the web, it's more common with MX5s though.


In the quest for cheap speed, I went on the hunt for smaller wheels. This will drop the centre of gravity without upsetting the suspension design, and effectively reduce the gearing which is the same as adding poowwweeerrrr. 10% in fact, if I could shoehorn some 195/45/14s on there as opposed to the stock 205/50/15s. Not insignificant...

I have a set of 13s that actually JUST fit, but they are worth as much as the car and probably too light, so not really appropriate sadly.

So, that led me to Facebook classifieds, and a set of unloved MX5s wheels a couple of miles away. All 4 tyres knackered, but the wheels actually in pretty good nick, 14" and only £50, so worth a punt. Armed with a tape measure, I had a check of the inner bore and thought they might clear - worth a punt anyway, and deal with any problems later 

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Picking them up revealed a funny smell. I have a suspicion the previous owner's dog had been using the stack as a pissing post! Still, a quick wash sorted that, then time for the moment of truth...

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They only bloody fit! Literally a mil to spare. I had to pull the wheel weights off to get the rears to go round, and even then the sticky residue scrubs the caliper!

Now on the lookout for tyres, not much choice in that size and all road tyres (which is what I wanted), so good value, fun in the dry, and safe in the wet.

Very interesting re the 14s fitting. What offset are the mx 'pissy' wheels?

Brimful of asha, I believe, same as the MR2 ones.

Weirdly, I can't find the ones I've bought in this list. Perhaps the UK spec wheels were different: http://www.jason-parker.net/images/wheels.htm

How would lowering the car to suit the 14" wheel affect things like driveshalt angles, control arms etc?

Going from 205/50/15ss to 195/45/14s: The car literally goes down by 1", with everything as it is (smaller tyres are half an inch reduction in radius, the wheels are another half an inch).

90mph at the limiter in 3rd gear becomes ~80mph, etc.

The point is that you don't have to lower the suspension (which upsets driveshaft angles, roll centres, etc), you simply lower the car as a whole.


On the power side of things...

Take 100Nm at the engine, going through 4th gear (1:1 ratio) and into a 4:1 diff (rounded numbers for ease), that gives 400Nm at the hubs.

A 205/50/15 tyre with radius 294mm therefore produces 1360N of forwards thrust at the tyre contact patch (torque = force x distance, rearranged).

A 195/45/14 tyre with radius 265mm provides 1509N - an increase of just over 10%.

The other way to do it would be to add ~15bhp to the engine, which is much more invasive and expensive!

Ideally I wanted 175/50/13s (ran these before on mx-engineinwrongplace  - AR1s) - that would have given 1587N / 17% - but not worth the cost here.

Quote from: AdamR28 on October 20, 2020, 08:44Going from 205/50/15ss to 195/45/14s: The car literally goes down by 1", with everything as it is (smaller tyres are half an inch reduction in radius, the wheels are another half an inch).

90mph at the limiter in 3rd gear becomes ~80mph, etc.

The point is that you don't have to lower the suspension (which upsets driveshaft angles, roll centres, etc), you simply lower the car as a whole.


On the power side of things...

Take 100Nm at the engine, going through 4th gear (1:1 ratio) and into a 4:1 diff (rounded numbers for ease), that gives 400Nm at the hubs.

A 205/50/15 tyre with radius 294mm therefore produces 1360N of forwards thrust at the tyre contact patch (torque = force x distance, rearranged).

A 195/45/14 tyre with radius 265mm provides 1509N - an increase of just over 10%.

The other way to do it would be to add ~15bhp to the engine, which is much more invasive and expensive!

Ideally I wanted 175/50/13s (ran these before on mx-engineinwrongplace  - AR1s) - that would have given 1587N / 17% - but not worth the cost here.

Good explanation. So i'd have to keep the ride height near stock and have the monster trucking look with big arch gaps. Suppose it would only be for track as I's use FL 15/16 for road.

Haha. Yeah good point on the arch gap thing. It's not something in my considerations at all but appreciate others don't want the 'off roader' look!

Looks like you will need a flame throwing guitar player chained onto the front!

https://www.youtube.com/watch?v=hRF-pgMWpwQ&ab_channel=AmiratheEccuyah

Got any plans to paint it?

Yeehaa, are you offering?

Nah, paint is too heavy. Rust is much lighter.

Quote from: AdamR28 on October 20, 2020, 15:33Yeehaa, are you offering?

Nah, paint is too heavy. Rust is much lighter.

That is not too bad a look to get around in London traffic. In the 80's I occasionally was asked to drive the Company's delivery flat bed transit, that was driven by all and sundry and looked decidedly the worse for wear, and it is surprising how gaps open up in traffic when you point the front end at too small a gap.
Only those that have driven in London will appreciate the validity of that.

I think a brushed on paint job using rustoleum combicolour would tie it all together.....

Quote from: Topdownman on October 20, 2020, 17:43I think a brushed on paint job using rustoleum combicolour would tie it all together.....

A small foam roller and Rustoleum made our garden railings look young again, goes on over bare metal, existing paint (and rust according to the manufacturer, but I did get most of that off) and has stayed there for for around 18 months in hot sun and freezing cold and all points in between.

I painted my old T4 van with it and put white primer on first with a roller. It left air bubbles in it though so I rubbed it down then switched to a brush for the top coat.

I always did regret leaving it in the primer as it looked like a golf ball with a slight rubbing down!

(As well as looking cool, it would have been very aerodynamic too...).

Strange, a roller typically suits a larger surface and a brush a smaller surface, but I found that the brush was going to take forever on the 12 mm bars and the roller really speeded up the process.

All this talk of paint... get out of my thread 

Seriously though, I completely agree on the merit of a banger. I'm currently also blasting around in a knackered old K11 Micra - can literally park it anywhere without worry, doors left open, nobody will go near it!


Bit of brake progress this morning - ripped all the pointless stone guards off (they were so rusty I did literally rip them off), pulled the servo and ABS out (about 5kg's worth).

Did some brake calculations (http://www.brakepower.com):

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Just need to modify the pedal box a little to increase the leverage of the pedal itself, and I'll find a way to use the standard master cylinder. Normally the master would sit centrally between those 4 holes, and those 4 holes are used to mount the servo.

I had eyeballed the spacing of the servo last night, and it looked similar to the master...

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Bingo!

Just a bit of chopping to do, and the master can be bolted straight to the pedal assembly, with a new clevis pin hole redrilled a bit higher up, and a bit of 'relieving' of the firewall.

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Also ordered all the stuff to make a manifold, looking forward to getting cracking with that! Figured either one of these two will be the easiest way to do it, and I can probably get away with just 8x 90 degree bends, 'manipulating' the tubing a little to get it to all fit and maintain matched header lengths.

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Snooping Spyderchat it appears this design should free up a fairly significant amount of power, especially in the 6-7k rpm range:

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Not sure if that's stock vs long 4-1 headers, or some sort of aftermarket vs the new header, but either way if I can have some fun playing with the welder and improve bhp/ton in the process, happy days.

I like your thinking on the brake master cylinder and pedal connection, seem to remember that arrangement.
Not to mention the manifold. If you jig it up you could start a side line supplying them.

Impressed with the work rate!

Some doods in the states stripped a Corvette to the tub similarly to your MunteR2:
https://youtu.be/Nt-JPcFM_Qg (Warning, they are very American,  a lot of burnouts, drag racin', and whoopin' and hollerin! But their engineering is solid)

They managed to get theirs down to 2550lbs (1150kg) from 3200lbs (1450kg) or a 20% drop, with roll hoop and harnesses etc. So I would say your weight target is certainly achievable considering on the 'vette, the core components would be a larger mass fraction due the fibreglass bodywork.

Also, are you going to shave those calipers?! That's some tight clearance! Especially when you add in a load of heat on track.

Shine on brother, great progress

Haha, thanks @iffyT 

Leroy looks funny. Chassis must be like a wet noodle! Impressive to get so much weight out though.

On the sly, my new target has been 750kg for a while now... having removed all the panels, and checked what weights they are, I think that's another 50kg come off. A few other bits I didn't account for originally, related to the bodywork, have added up to a few kg too. We'll see soon enough!

Calipers... I'm not sure. It is awfully close. I think I'll blast around the industrial estate here and see what it's like, any rubbing will be obvious. There is plenty of meat on the calipers though, so skimming a mil or so off with the flap disc won't be an issue.


Brake pedal is also now back in, everything lines up nicely. Still have a bit of adjusting to do of the brake light switch and clevis once the brakes are bled up, but access is good.

New push rod made from an MX-5 suspension bolt, with the end rounded off into a ball by sticking it into the drill and flap disc-ing the end down.

Also found an old MTB dropper seatpost rubber boot which was the perfect size to go over the master and keep water out - normally it's hidden away inside the servo!

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Like a glove    Only had to enlarge the hole slightly, the shape of the master and reservoir fit around that join in the shell panels perfectly.

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Quote from: AdamR28 on October 21, 2020, 15:24Leroy looks funny. Chassis must be like a wet noodle! Impressive to get so much weight out though.

That wet noodle now has 1500bhp+ and runs 7s... It must be quite a ride!
They seem to know how to build stuff (unlike a lot of youtubers) as they've done several hundred drag runs and the engine has never needed to come out (so they say).
I'm sure they had to add a load of buttressing, backing plates etc all over that chassis which would have added weight. Although tbf the C5 Corvette lends itself well to this as it's essentially an old school body-on-frame, crossed with some build elements in common with space-frame race cars. It's fairly stiff.

Ah! I didn't know about any subsequent development, just watched a bit of the video you linked to; sounds like it's come on leaps and bounds then. One to stick on my to-watch list - thanks!

Koni inserts fitted this morning, ready to go back on with a set of almost-new 2nd hand Tein springs. I think these are going to need cutting down - the front of the car is nearly 2" higher than stock ride height due to all the weight that's been taken out!

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This is a pretty straightforward job, you just have to be brave and go for it - but obviously remember you can take off, but not put back on easily...


It's a good job I'm a man and ignored the instructions... my rears came with paperwork for the fronts! It said to cut 65mm off, which would have left me pretty snookered.

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In the end, about 30mm was cut off the rear, compared with 65mm ish at the front.

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If anyone stumbles across this and is about to partake on fitting a set of their own, feel free to give me a shout for a confidence booster / tips.

Good choice of suspension same as i have ,  with your lower weight the spring rate should be ok as i find it a bit soft for me on my full weight car on track, be interesting to see ride height as again i think its a bit low on my car for bumpy back road hooning anyhows

Yeah man, I think the Koni Sports are an excellent damper - have had them on another car before, also with lowering springs. I rate them as kind of 'OE Plus', a quality unit with proper damping curves, rather than far eastern anodised bling which looks pretty but doesn't allow the wheels to move up and down properly!

I measured ride height on standard springs / wheels at 155mm front and rear from the ground to bottom of sill pinch weld, so obviously that will put a standard car at around 125mm on -30 lowering springs.

I figure I'm dropping 25mm from the smaller wheels / tyres, making 130mm ride height, then if the suspension is lowered a smidge on top of that to get to 115mm ish, that's a good place to be for track only use - hopefully meaning I won't be running into the bump stops all the time. That said, the NA Miata is designed to run on the bump stops in full lateral loading, so I won't be disappointed if that happens.

Shocks back on and onto the floor at lunchtime. Ride height approx 160mm as it stands but that's with stock sized wheels / tyres, so it is effectively 135mm at the moment. Higher than standard even on -30mm lowering springs - it must be light, ha!

There is plenty of travel left before the bump stops, about 35mm up front and 50mm at the rear (on the damper - therefore a touch more at the wheel), so with that in mind I'll chop a coil off the top of each spring. The top couple of turns sit coilbound so this is completely safe. After that, I'll let them settle and see where its at - likely 120mm ish, which will leave the rear lower wishbones parallel with each other and the floor, perfecto!

Nice work on the Konis! I'm in the process of doing the same, but I've hit a snag... cross-threaded one of the retaining nuts and I'm in the process of helicoil repairing it. Sadly I don't think it's worked. I might need the help of someone more experienced

Would love to hear how your feedback on them when you've had a chance to road test.

P.S. did you trim the front bump stops? My understanding is that's what most here do when using any lowering springs.