|LIFE OF A GT|
|April 26, 2008 - One of the steering boots was broken, so it got replaced.|
Easy enough, although the "precision engineered" replacement from NAPA (it said so on the box!) was anything but. It was a bit of a fight to get the undersized small end over the surprisingly hefty tie rod, but I won. I always win. It's just depends how badly the car has to lose.
entry 49 - tags: steering, suspension
|January 28, 2009 - The next step is the steering rack mounts.|
To behind, a fair bit of careful measurement. I want to try to minimize bumpsteer, and the best way to do that is to start with the factory Mazda location and then work from there once the suspension is assembled. I duplicated the factory brackets using a piece of 1x3 rectangular steel. A plate on the bottom will provide some lateral strength.
entry 157 - tags: steering, frame
|February 1, 2009 - Time to mount the steering rack, umm, mounts.|
I'm still just tacking everything in place, but it's almost time to commit. I did chop a bit of extra frame rail off the sides to clear the rack itself, this was always part of the plan - I figured it was much easier to make them shorter than longer.
entry 159 - tags: steering, frame
|February 1, 2009 - This cut in the steering crossmember was required to clear the pinion housing on the rack.|
It's a bit ugly, these were the chops made to get the clearance I needed.
entry 160 - tags: steering, frame
|February 1, 2009 - Once the final clearance was sorted out, I squared off the cut.|
entry 161 - tags: steering, frame
|February 1, 2009 - A small piece of steel was welded in to close up the cut.|
It's actually a spare piece of frame rail, the sizing was perfect. Voila, clearance! Once it's welded in completely, I'll clean up the edges with a grinder so it sits flush with the rail.
The steering crossmember could have been smaller, but I wanted the 2x3 tube to give me lots of twisting stiffness for the front of the frame (more than I'd get with a round tube) and to give me a nice flat surface to weld bracing to. Ideally, it should have been 2x2 for packaging purposes so I wouldn't have to do things like this. But that's okay, I think this will end up better overall.
entry 162 - tags: steering, frame
|February 2, 2009 - Remember the steering crossmember that really should have been 2x2?|
Well, it's getting closer. To ensure as much oil pan clearance as possible, I had to take a chunk out. Right about an inch at the back and nothing at the front.
entry 168 - tags: steering, frame, clearance
|January 24, 2010 - Next challenge: the steering column.|
I'm trying to deal with all of the major packaging problems right now. And this is a good one - the universal joint from the MG that bolts on to this column is so big I can't even slide it into place. It hits the head. As an added bonus, the shaft is a considerably larger diameter than the Miata one at the steering rack.
entry 262 - tags: steering, packaging
|January 24, 2010 - The first possible solution I came up with to the steering column problem was my standard go-to option.|
What about a Miata? So I grabbed a Miata column, stuck a wheel on it (I have at least three wheel adapters and a range of wheels that will fit) and started measuring. Turns out it's ridiculously good.
It doesn't look like in the picture, but the lower side of the bracket on the end of the Miata rack lines up with the location of the firewall on the MG. Easy alteration and the lower mount is done. The flat plate that serves as the upper bracket is actually in exactly the right place. Depending on the wheel adapter I use, the two holes on the Miata mounting plate are in the same place as the MG ones. Well, they're about 10mm closer together than on the MG. But this is a very solvable problem. The third mounting point would be easy to add. And the overall length is shorter, which will move that awkward U-joint further up.
entry 263 - tags: steering, packaging
|January 25, 2010 - Just for fun, I checked the length of the lower section of the Miata column.|
After all, it's designed to bolt directly into the steering rack. I couldn't believe the result. It's perfect. Not just "close", but bang on perfect. The universal joint tucks into the recessed spot in the firewall, and the rest of the column inside the car is in the correct spot. This could not be better, I really lucked out.
Inside the car, I can play with the final location of the wheel using my various adapters. I'll use the Miata combo switch (ie, stalks) to control the turn indicators, lights and - yet another bonus - the cruise control from the Camaro. I don't think it'll look too anachronistic in the MG interior, and the Miata parts both feel better than the MG ones and give me the controls I need instead of requiring a bunch of extra switches on the dash.
I still can't get over how well this works.
entry 264 - tags: steering, packaging
|January 25, 2010 - Another shot of the proposed steering column routing.|
It looks as if it'll be fairly simple to arch the exhaust out a bit and run the column between the header and the block.
entry 265 - tags: steering, exhaust
|February 9, 2010 - Time to get some work done on the car!|
I started by removing the lower universal joint from the steering rack and welding it to the shaft. There simply wasn't enough room for the cross-bolt used in the original clamp design, the bolt would hit the motor mount.
entry 276 - tags: steering
|February 9, 2010 - A peek at the clearance.|
This is post-fix, before it was tighter! Installing the steering column is a bit of a pain. I had to lift the engine up, remove the rack, install the shaft on the rack, slide the whole thing back in to place and let the engine back down. I'm trying to make it easy to work on this car, but there's only so much I can do.
That motor mount bracket isn't fully welded yet. That'll happen when the engine comes out next time.
entry 277 - tags: steering, packaging
|February 9, 2010 - I wanted to do an ergonomics check, so I installed the driver's seat to see how everything was working out.|
The gas pedal was held in place by a vice grip, the brake pedal return spring kept that in the appropriate place and the steering column was clamped on. The initial fit showed that the steering wheel sits very low. That's odd, given that my various collection of test wheels are all significantly smaller than the original. When I checked the MG column against the Miata one, I realized the difference was due to the bracketry on the column. With that taken into account (as seen here), the wheel was just about perfect. It needs to come a bit closer to the driver to be ideal, but that's easy.
The shifter is perfectly placed and everything feels good. I think it'll be a good driver. Don't mind the steering wheel, that's just one of the testing units. Although it's not exactly offensive.
entry 279 - tags: ergonomics, steering
|February 14, 2010 - I wanted to see how the Miata steering column would sit with the dash.|
My concern was that the location of the column would leave bare metal exposed. Well, that's not a problem. With the length of the unmodified Miata column, the standard column shroud is an almost perfect fit! I'll have to trim the bottom a bit to clear the shape of the dash, but that's easy. I'd also been worried the Miata parts wouldn't match the MG interior, but I think it's going to blend in really well.
In the picture, it looks as if it's hiding one of the gauges a bit. It doesn't look that way in person, but this is a 1999-05 shroud. I can also use from from a 1990-97 model, which is a little bit more square and might give a little more clearance.
The steering wheel will need to be a bit of a deep dish style to match the MG distances. But that's easy to do later as I fine-tune the ergonomics.
entry 283 - tags: ergonomics, steering column
|February 14, 2010 - Mounting the steering column was easy enough.|
I drilled out the spot welds holding the bracket to the MG column, and simply transferred it to the Miata part. It's just tack-welded here for a final test fit.
And with this, the steering column is finished. The car will sit on its wheels and can be steered. Progress is being made.
entry 284 - tags: steering column
|August 31, 2010 - I'm often accused of having an unfair advantage when building cars because I work at Flyin' Miata.|
The advantage is access to exotic tools and knowledge. I've discussed the exotic tools before, but what about the knowledge? Well, I spend all day sharing that knowledge with other people, but it is coming in handy at this step.
I needed to hook up the power steering lines. A GM pump and a Miata rack. Luckily, this is the exact combination used in the V8 conversions at FM. So I used my special insider knowledge and went to the FM website to get a parts list of what I'd need. Yup, special insider knowledge that's shared with the entire world!
These two parts are the adapters to convert the fittings to common AN-6 ones. The one the right is specially machined to mate with the flare on the Miata rack, the one on the left is off-the-rack with a special washer as the usual o-ring doesn't seal. My advantage was that I didn't have to order them and wait for the parts to arrive, but I was able to simply go pick them off the shelf for instant gratification. I'm still missing one 90 degree adapter - the different packaging of my setup requires different hose routing - but it's almost all hooked up now.
entry 380 - tags: steering
|August 31, 2010 - I may not need it, but I fitted a cooler to the power steering loop.|
It's a small transmission cooler. It's anchored at one end to the support under the hood latch and supported by the power steering lines on the other. Works nicely. The fins are pretty fragile so I've wrapped it in cardboard to protect it for the time being.
entry 382 - tags: steering
|September 7, 2010 - The new brake master cylinder is here.|
I did some calculations a while back on brake master sizes, and the ideal (to match the Miata) ended up being 15/16". My plan to use the Miata booster fell through due to a critical lack of space. Well, I have the choice of the old 7/8" setup from the MG or a 1" Wilwood caliper. Since almost everyone prefers a hard pedal with a bit more effort to a softer one, I've decided to go with the Wilwood setup. This also means I don't have to mess around with British flares! I'm not going to bother with the brake plumbing yet, but since the master arrived I just had to bolt it in.
I also bled the clutch hydraulics, so I should theoretically have a functioning clutch. I don't have any way to tell for sure yet - I'll wait until Janel is around, then see if I can spin the driveshaft by hand when the clutch is depressed. Oh boy, I sure hope so. It feels good anyhow.
The power steering lines are also fully hooked up now. By this point, all the fluids in the car (other than the brakes) should be contained. So it's back to wiring...
entry 392 - tags: clutch, brakes, steering
|December 20, 2010 - Time to find out why the steering feels a bit odd.|
It doesn't have much self-centering and almost feels as if there's too much friction in the system somewhere. Step one: lift the front wheels off the ground and get a feel for it. Step two: start removing various components to find the friction. It's 100% Miata steering, so it should work well.
The first thing I pulled off was the steering wheel and compared it to a stock Miata unit. Bingo. Nice and free movement. Wow, that was easy to find. Experimentation with a few other wheels (yes, there are five on the workbench) traced the problem to an adapter that had slightly oversize splines. This let it slide too far down on the column and put a lot of pressure on the turn signal canceling mechanism.
entry 512 - tags: steering
|December 20, 2010 - The solution to the bad adapter was to replace it.|
This unit - of unknown origin - would bottom out a full 1/2" higher up on the column, avoiding the problem. But it was both too short and had the wrong bolt pattern for the wheel. So I cut both apart and welded them together using a piece of pipe as the spacer. Nice and solid, and with some attention to detail everything is parallel and centered. There's a rubber boot that slips over this so you can't see it.
A quick test drive showed a massive change in the steering feel, with good centering and lighter effort. Time well spent.
entry 513 - tags: steering
|June 12, 2012 - Time to work on steering.|
I've been trying to track down some free play in the steering wheel. It's definitely not the tight, responsive steering it should be. It appeared to be in the rack itself. First I tried adjusting the rack to see if that would help, but no. So today was spent pulling out the old rack and slotting in a replacement. It was a bit of a challenge, one of the bolts was almost completely inaccessible with the engine in place. One custom-length socket later and it succumbed!
On a quick drive around the block, the new rack appears to be a success. We'll see how it feels on a longer drive tomorrow.
entry 646 - tags: steering
|June 12, 2012 - Another steering tweak.|
The steering feels overassisted - it's too light for my taste. I have a few things to learn about power steering systems in terms of the results of different pressure versus different flow, but the RX7 crowd seem to think that trimming the relief spring should drop the pressure a bit. Others claim that the only real solution is a Turn One pump for $240.
The spring cut makes logical sense to me - and if it doesn't work out and I end up going for the Turn One setup, it doesn't make any difference. So I made the cut. A fairly conservative one at that. It's not a massive change, but there is a bit more meat to the wheel. I might try one more little snip later, but first I'll drive it for a bit to get used to the new rack and assist.
entry 647 - tags: steering
|January 5, 2014 - The MG's seen some action.|
First, I took it to the track again. I finally got the chance to see how it handled at the limit without the big fireballs. The answer? Not that well, really. The car was oversteering badly, feeling like an arrow flying backwards. On the sweeper, it was actively trying to kill me constantly. The steering still had the wobble in it I didn't want. I tried adjusting the rear suspension pickup points (based on something I came across in Mark Donohue's "Unfair Advantage", of all things) and it helped a bit. But it was still twitchy and difficult to even drive on the interstate without the car exhibiting roll steer.
But I noticed something. The front tires were worn as if I had significant toe in. Lots and lots of it. So I checked, and sure enough. The toe was way out. I fixed that and all of a sudden the car was much better. The odd roll behavior went away and the steering dead spot disappeared. All of that chasing around, and it was just a bad alignment. Which is odd, given that it's been aligned before...
I also took the car out to a Corvette autocross, which they found fairly entertaining. Unfortunately, I simply didn't have enough tire to deal with the torque of the engine on a first-gear course and finished 4th overall if memory serves. Still, it was a fun day.
So it's mostly a driver right now. There are still some things that need to be sorted - in particular a vibration from the transmission leaning up against the tunnel under load and the bad reverse selection - but those don't stop me from driving it. That steering problem really took the fun out of it. That's been sorted!
entry 648 - tags: track, steering, handling, autocross