Are stretched tyres safe and legal?
In many ways, the tyre industry is fortunate in that no sub-standard new tyres have found their ways into the UK marketplace. While tyre performance varies considerably between brands, not one new tyre fails to meet the mandatory Type Approval standards, unlike bulbs for example. However, we all rely on experienced tyre fitters and even the best tyre can be rendered dangerous, if it is not mounted properly to the wheel rim.
The increasingly-popular trend of ‘stretching’ (fitting narrow tyres to a wide wheel rim for aesthetic purposes) has introduced a safety conundrum and legal confusion. Tyre manufacturers have commented that they are not in favour of the practice, because excessive stretching places the sidewall under extra stress, which is not considered as part of the tyre’s design. The British Tyre Manufacturers’ Association concurs and adds that, in such cases, there is a serious risk of the tyre being dislodged from the rim under sudden cornering forces. Therefore, it is reasonable to conclude that over-stretched tyres are unsafe.
Supporters of stretched tyres comment that they are not illegal but fail to consider that an MoT pass does not mean that Construction and Use (C&U) offences are not being committed. Any vehicle that no longer complies with C&U is, legally, not roadworthy and this liability falls upon the driver, which is likely to translate into invalidated insurance.
The DVSA issued advice to MoT Testing stations earlier this year, stating that stretched tyres should fail the annual inspection, if the tyre is not seated correctly on the rim; even if the tyre neither protrudes excessively from the wheel-arches, nor rubs against the bodywork. The diagram at the top of this blog demonstrates the reasons for a test fail, because of the gaps between the tyre’s bead and rim (circled). Yet, even if a pass certificate is issued, the DVSA advises that an offence may still be committed.
Obviously, our advice is to avoid stretched tyres altogether. If you really must fit wider rims, the best way to stay on the right side of the law and be safe is to consult your chosen tyre manufacturer for its official stance on wheel width recommendations, especially if the advice is approved by the European Tyre and Rim Technical Organisation (ETRTO). Nankang Tyres, for example, produces an interesting leaflet here that gives the maximum rim width that can be used according to its tyre sizes.