Smart Car of America Forum banner

1 - 20 of 36 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
I would like to put larger wheels and tires on my car and want the same size all around.
I have considered the wheel adapters (3 to 5 lug), but have heard that they are not really strong enough for everyday use. Has anyone considered simply re-drilling the hubs and rotors/drums for a different pattern? Are the hubs of a design that would even allow this?
I will be buying new tires soon and would like to do everything at once if possible.
 

·
Registered
Joined
·
5,192 Posts
This is the back side of the hub. There isn't enough meat to drill another pattern. Only in the raised cast areas where the stock holes are is it thick enough. On top of that if you superimpose another pattern you will find one or more of the existing holes will interfere with the pattern no matter how you turn it. There are whole threads on this, been beat to death. There are plenty of aftermarket wheels in almost any size you could need. You can get adapters for 5 x 112 Mercedes to 3 x 112 smart.
 

Attachments

·
10Year+ Supporting Member
Joined
·
3,455 Posts
I run 7.5x17 Brabus wheels with 215/35-17 Hankook tires all around on my '09 Brabus coupe. They are plenty big and I have no issues with rubbing or electronic nannies. I was told by Discount Tire if you come in with spacers, they will do no work on your car until the spacers are removed. Not even repair a flat. Just something to keep in mind.
 

·
Registered
Joined
·
13 Posts
This is the back side of the hub. There isn't enough meat to drill another pattern. Only in the raised cast areas where the stock holes are is it thick enough. On top of that if you superimpose another pattern you will find one or more of the existing holes will interfere with the pattern no matter how you turn it. There are whole threads on this, been beat to death. There are plenty of aftermarket wheels in almost any size you could need. You can get adapters for 5 x 112 Mercedes to 3 x 112 smart.
I hate to dig up an old thread, but has there been any more information about redriling the hubs and rotors to go to 5x112? That seems like a good way to get to 5-lug without causing wheel offset issues.

I'm considering doing this to mine and just wanted to see if anyone else had tried it.

I'm not concerned about adding material on the back side of the hub for thread depth. That's not an issue.
 

·
Registered
Joined
·
465 Posts
I think the conclusion is: don't re-drill the hubs, get a 3 to 5 bolt adapter. You then need to make sure you get rims with the correct offset to match compensate for the thickness of the adapters.
 

·
Registered
Joined
·
13 Posts
I think the conclusion is: don't re-drill the hubs, get a 3 to 5 bolt adapter. You then need to make sure you get rims with the correct offset to match compensate for the thickness of the adapters.
Thanks for the reply, but I would like to hear some actual reasons that this isn't possible. From everything I see, it does not look like a lot of trouble, but I could be missing something, which is why I would like to hear from someone who has done or attempted to do this.
 

·
Registered
Joined
·
465 Posts
I haven't heard of anyone actually doing it. I think you would weaken the hub too much. It's surprisingly thin material.

If you look in the photo above, you will see that where the current holes are, there is extra material thickness. This provides strength as well as providing sufficient number of threads to hold the bolts - neither of which you would have if you drilled more holes in it. What would happen is the hub would deform and then effectually break under load and there would be a high risk of the wheel bolts pulling out.

Having worked in automotive manufacturing for 10 years and having worked in manufacturing R&D consulting for 8 years, I would say this is a bad idea! Under no circumstances should you try this!

The hub is made from a forging (not a casting), which is even stronger than billet. So, even if you were to have a custom made hub with 5 holes, it would have to be substantially beefier than the original design in order to meet the same strength characteristics.
 

·
Registered
Joined
·
13 Posts
I haven't heard of anyone actually doing it. I think you would weaken the hub too much. It's surprisingly thin material.

If you look in the photo above, you will see that where the current holes are, there is extra material thickness. This provides strength as well as providing sufficient number of threads to hold the bolts - neither of which you would have if you drilled more holes in it. What would happen is the hub would deform and then effectually break under load and there would be a high risk of the wheel bolts pulling out.

Having worked in automotive manufacturing for 10 years and having worked in manufacturing R&D consulting for 8 years, I would say this is a bad idea! Under no circumstances should you try this!

The hub is made from a forging (not a casting), which is even stronger than billet. So, even if you were to have a custom made hub with 5 holes, it would have to be substantially beefier than the original design in order to meet the same strength characteristics.
I don't disagree anything you have said, but I still find it hard to believe that someone hasn't created a good, strong 5-lug hub/rotor/drum system for these cars. Broaching splines on a well built, quality hub is not rocket science.

I missed the initial Smart car craze and have only gotten into it now because of my need to transport one on the back of my "RV Hauler". However, I'm blown away that the 3-lug issue still exists after all of the years these things have been on the road.
 

·
Registered
Joined
·
465 Posts
A custom built one could be done, but not as a forging because it wouldn't be cost effective due to the small volumes - forging requires a skilled engineer to design the die to the proper specs, then you have to have the die made and find someone to do the forging. If you could find a 5 bolt hub with comparable dimensions, it might be as simple as a little machining to make it fit - that's if you can find one.

The adapters are just a more viable solution - very cheap and easy to make with very little upfront cost - almost anyone with limited CAD skills could do it - then you just send it to a machine shop to get made or make it in your garage if you have a lathe and a mill. I'm considering making my own because the available ones I've seen are just way overpriced.

Once you have a 5 bolt pattern, you have a wide range of options for offsets.
 

·
Registered
Joined
·
13 Posts
A custom built one could be done, but not as a forging because it wouldn't be cost effective due to the small volumes - forging requires a skilled engineer to design the die to the proper specs, then you have to have the die made and find someone to do the forging. If you could find a 5 bolt hub with comparable dimensions, it might be as simple as a little machining to make it fit - that's if you can find one.

The adapters are just a more viable solution - very cheap and easy to make with very little upfront cost - almost anyone with limited CAD skills could do it - then you just send it to a machine shop to get made or make it in your garage if you have a lathe and a mill. I'm considering making my own because the available ones I've seen are just way overpriced.

Once you have a 5 bolt pattern, you have a wide range of options for offsets.
My issue with the adapters is solely the added backspacing. That reduces the wheel choices quite a bit.

What do you not like about the adapters currently on the market?
 

·
Registered
Joined
·
465 Posts
I don't see the back spacing as an issue. I shopped around for rims and saw ample offset choices.

Price is the only thing I don't like about the current ones on the market. They seem to be around the $400 mark, which to me seems absurd. The material for each set is probably about $10 + bolts and probably about 5 minutes machining time/pc + set up. I could probably sell them for $100 for a set of 4 and still make 30 points.
 

·
Registered
Joined
·
13 Posts
I don't see the back spacing as an issue. I shopped around for rims and saw ample offset choices.

Price is the only thing I don't like about the current ones on the market. They seem to be around the $400 mark, which to me seems absurd. The material for each set is probably about $10 + bolts and probably about 5 minutes machining time/pc + set up. I could probably sell them for $100 for a set of 4 and still make 30 points.
You lost me there. Personally, I don't want my name attached to any products that have to do with road driving. It's one thing to make something for myself, but it's not worth the liability to produce them for public sale.

I spend a lot of time in Solidworks. Drawing them is not an issue, but drawing a one-off set for personal use doesn't make sense if I value my time any. Cheaper to just buy a set.
 

·
Registered
Joined
·
465 Posts
When you refer to backspacing, are you referencing the affect on offset? This is the distance that the wheel mounting face would be moved out, which would be the thickness of the adapter - approx 20mm. Just want to make sure we're talking about the same thing here.

On stock offset rims, 20mm wouldn't be an issue for most people because the new fitment is typically preferred: the wheels stick out an additional 20mm which actually looks a little better.

When going to wider rims, then you would have to do a little math to figure out what would look best.

The other benefits of adapters are that you have one solution for both front and back, and it's a quick switch back to stock, which is good if you have stock rims for your winter tires.
 

·
Registered
Joined
·
1,635 Posts
I don't disagree anything you have said, but I still find it hard to believe that someone hasn't created a good, strong 5-lug hub/rotor/drum system for these cars. Broaching splines on a well built, quality hub is not rocket science.

I missed the initial Smart car craze and have only gotten into it now because of my need to transport one on the back of my "RV Hauler". However, I'm blown away that the 3-lug issue still exists after all of the years these things have been on the road.
The issue is not a lack of ability to fabricate what you describe but a lack of potential demand to make the investment worthwhile. Not many smart cars on the road in relative terms and not many of those would pay the cost for special hubs and five-bolt wheels.
 

·
Registered
Joined
·
465 Posts
Precisely. Such modifications attract much fewer buyers because people don't like to modify these types of components. Adapters on the other hand are non-invasive and are easily switched back by anyone who can operate a wrench and a floor jack.
 

·
Registered
Joined
·
13 Posts
When you refer to backspacing, are you referencing the affect on offset? This is the distance that the wheel mounting face would be moved out, which would be the thickness of the adapter - approx 20mm. Just want to make sure we're talking about the same thing here.

On stock offset rims, 20mm wouldn't be an issue for most people because the new fitment is typically preferred: the wheels stick out an additional 20mm which actually looks a little better.

When going to wider rims, then you would have to do a little math to figure out what would look best.

The other benefits of adapters are that you have one solution for both front and back, and it's a quick switch back to stock, which is good if you have stock rims for your winter tires.
Yes, we are talking about the same thing.

I agree that 20mm won't end the world, but if I could avoid that along with wheel spacer issues, that would be a win win for me.

I'm also still a little perplexed that you favor the strength of two very small (less than 8mm - bolt head is 12mm - McMaster-Carr) slices of aluminum and one bolt, holding on your wheels, using the spacers, over a larger chunk of billet steel, when using a properly machined billet steel 5-lug hub. The amount of aluminum at the weakest point on the adapters is pretty thin (under the adapter bolts that secure it to the hub).
 

·
Registered
Joined
·
13 Posts
Precisely. Such modifications attract much fewer buyers because people don't like to modify these types of components. Adapters on the other hand are non-invasive and are easily switched back by anyone who can operate a wrench and a floor jack.
Agreed, but there are people out there going to great extents to get crazy wheel combinations on these things.
 

·
Registered
Joined
·
465 Posts
The adapters are made out of steel, whereas spacers are often made out of aluminum. Adapters typically have two bolts holding the adapter to the hub and one bolt through from the rim to the hub; therefore held by 3 bolts. The remaining 4 bolts in the rim anchor into the adapter. I don't see any reduction in strength here.

Threads in the steel adapters should be roll-formed to maximize strength.

Aluminum is not a suitable as a material for an adapter, not enough yield strength.
 

·
Registered
Joined
·
13 Posts
The adapters are made out of steel, whereas spacers are often made out of aluminum. Adapters typically have two bolts holding the adapter to the hub and one bolt through from the rim to the hub; therefore held by 3 bolts. The remaining 4 bolts in the rim anchor into the adapter. I don't see any reduction in strength here.

Threads in the steel adapters should be roll-formed to maximize strength.

Aluminum is not a suitable as a material for an adapter, not enough yield strength.
So you're saying that less than 10mm of steel is not a reduction in strength as compared to the thickness of the hub for those same two bolts? Honestly, I don't care either way. I'm trying to avoid the adapters if possible. I will probably buy three lug wheels before going with the adapters. I'm not racing the car or driving it hard anyway.
 
1 - 20 of 36 Posts
Top