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Speak to one of our experts.
23 July 2025
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You’re not alone if you’ve ever heard a clunk from the rear of your MX‑5 MK4 or RF when passing over potholes or uneven surfaces. A well‑known Achilles’ heel of the MK4 is the rear hub‑carrier bushes (which are spherical bearings) – Mazda doesn’t sell them individually. Your only OEM fix?Fitting a complete hub assembly on both sides at over £400 each (plus £160/hour labour), totalling around £1,600 all in – SEE MX5 Forum Post
— from MX‑5 Owners Club
Owners frequently report hearing a distinctive knock or rumble from the rear suspension—that’s the failing spherical bearing inside the hub.
OE References: N243-26-11X, N243-26-11XA, N243-26-11XB, N243-26-12X, N243-26-12XA, N243-26-12XB, N243-34-300, N243-34-350
Sealed Spherical Bearings
These contain a spherical bearing with rubber seals. Over time, those seals degrade, allowing water, grit, and grime in. The result? Premature wear, excessive play, and that dreaded rear clunk forum.mx5oc.co.uk.
No Spare Bush Supply
Mazda doesn’t offer the spherical bushes separately, forcing you down the costly full‑hub route
Design
The spherical design, although space-efficient, fails to resist contaminants in the long term, as evidenced by the hub issues that appear even at low mileages (20–40k miles).
Polybush 27AL is a bespoke polyurethane replacement kit that resolves the issue at its root.
Polyurethane lasts 6× longer than rubber or standard bushes; not affected by oil, water, or petrol, and resists abrasion and compression set
https://www.youtube.com/watch?v=gPM2LCndLWg
Precisely engineered durometers (hardness levels) deliver smooth suspension movement and outstanding alignment retention.
Internal mild‑steel, zinc‑plated inserts prevent corrosion, just like OEM—but without the rubber seal flaws mx5parts.co.uk.
Available as a part set for both sides —no hub swap needed
“The bushes are 27AL Blue from Polybush”
— from a YouTube guide
“A fantastic saving on having to replace the whole rear hub.”
— John Foster, MX‑5 Parts crowned review
“Mazda don’t sell them as a standalone part…you have to replace the entire hub carrier”
— forum user “ckyliu”
These aren’t one‑off cases—thousands of MK4 owners (and even Mazda dealers) now depend on 27AL to resolve rear‑end noise, grip issues, and misalignment without breaking the bank.
| Feature | OEM Spherical Bearing | Polybush 27AL |
|---|---|---|
| Replacement cost | £400+ per hub | ~£185 per set (4) |
| Labour costs | 4 hours @ £160/hr ≈ £640 | ~2 hours DIY or circa £200 professional |
| Total cost | £1,600+ | ~ £389 fully fitted (DIY + parts/labour) |
| Longevity | Short‑lived rubber seals | 6× lifespan; non‑compressing polyurethane |
| Alignment stability | Wears quickly, misaligns fast | Holds camber/toe like new |
| Ride feel | OEM spec | Marginally firmer, but still retains the original, precise & comfortable drive |
Parts & labour DIY total ≈ £389 versus £1,600+ dealer job—a ~75% saving.
Even if you pay a trusted independent workshop £200 for fitting, your total budget is under £600 all in.
Alignment stays sharp, tyre wear is reduced, and your MX‑5’s handling remains crisp, not squirrely.
Polyurethane bushes, especially 27AL, create a far tighter suspension geometry than worn spherical bearings. What do drivers notice?
No bounce or “clunk” coming out of corners or bumping over speed humps.
Sticky grip under acceleration and braking—less squat and roll.
Control maintained miles into misaligned OEM replacements.
We back 27AL with:
Clear fitting instructions and photo guides.
Walk‑through videos (e.g., Polybush Rear Hub Carrier install on YouTube)
Polybush support—thousands of installs and counting.
Even Mazda franchises source from us—saving techs time and cost vs OEM hubs – OE Reference: N243-26-11X, N243-26-11XA, N243-26-11XB, N243-26-12X, N243-26-12XA, N243-26-12XB, N243-34-300, N243-34-350
Q: Will it make the ride overly stiff?
A: Not at all. 27AL is engineered with the ideal (hardness) durometer. As one forum member noticed: “Ride quality and comfort continue to be excellent too, so there’s no compromise…”
Q: Does it squeak like some polyurethane bushes?
A: No. Polybush’s comfort/blue kit is designed not to squeak—and installs handily with dish soap, as Michelin‑tested backers confirm.
Q: Is it DIYable?
A: Absolutely—it’s a weekend job for a mechanically‑minded owner. But a hydraulic press speeds things up.
If you own an MX‑5 MK4 or RF, the rear hub bush/spherical bearing is a ticking time bomb. Mazda’s only fix is an expensive hub swap—but with Polybush’s 27AL it, you can:
Save around £1,000+ on parts and labour
Eliminate rear clunks and restore solid control
Keep alignment tighter for longer
Get top-tier, corrosion-resistant, long-lasting performance
We provide full fitting instructions, videos and expert backing. Thousands of happy customers— and even Mazda garages—have already chosen 27AL.
Don’t wait for the knock. Act now, fit 27AL, and enjoy your MX‑5 like it’s fresh out of the showroom.
Ready to order?
Rear Hub Carrier Upper & Lower Trailing Arm Bush Blue – Abarth | Fiat | Mazda – MX5
